Patent Publication Number: US-11649028-B2

Title: Watercraft having an interface for mounting a propulsion mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation in part of U.S. patent application Ser. No. 17/089,639, filed Nov. 4, 2020, which is a continuation of U.S. patent application Ser. No. 16/287,989, filed Feb. 27, 2019, both titled “INTERFACE FOR MOUNTING A PROPULSION MECHANISM TO A WATERCRAFT,” now U.S. Pat. No. 10,829,189, and this application claims the benefit of U.S. Provisional Patent Application No. 63/153,357, filed Feb. 24, 2021 and titled “INTERFACE FOR MOUNTING A PROPULSION MECHANISM TO A WATERCRAFT,” all of which are hereby incorporated by reference herein in their entirety. 
    
    
     TECHNICAL FIELD 
     The invention relates to an interface for mounting a propulsion mechanism to a watercraft, and to a watercraft that includes such an interface. 
     BACKGROUND OF THE ART 
     Various pedal operated propulsion mechanisms exist for propelling watercrafts such as kayaks. Such pedal operated propulsion mechanisms are becoming increasingly popular in fishing kayaks since users can propel their watercraft using only their feet while their hands remain available for holding fishing rods and the like. 
     One type of pedal operated propulsion mechanism comprises a pedals that operatively connect to a pair of flappers adapted to oscillate through arcuate paths in a generally transverse direction with respect to the central longitudinal dimension of the watercraft. Such pedal operated propulsion mechanisms are typically mounted to a receptacle in the hull or body of the kayak. In these designs, the pedal operated propulsion mechanism is directly supported by and coupled to the hull of the kayak. While this configuration may be suitable in many instances, the reciprocating movement induced on the pedals tends to urge slight movement of the foot propulsion mechanism relative to the hull of the kayak, which causes damages to the hull over time. Since the hull itself defines the support for the foot propulsion mechanism, the entire hull must be replaced when such damage occurs. Furthermore, the manufacturing of such a hull by thermoforming may prove onerous since the crafting of the receptacle for the propulsion mechanism typically requires a worker to carefully cut out the opening for receiving the foot propulsion mechanism, which tends to slow down the manufacturing process. 
     Therefore, it would be desirable to be provided with an interface for a watercraft that alleviates at least some of the above-identified drawbacks. 
     SUMMARY 
     According to a broad aspect, there is provided an interface for mounting a propulsion mechanism to a watercraft including a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion. In this broad aspect, the interface comprises: 
     a first portion including a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about the periphery of the well, and at least one channel extending from the second plate, the channel being positionable in the well, in registry with the hole of the first portion, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; and 
     at least one fastening assembly for removably fastening the first portion to the body of the watercraft. 
     In one feature, the interface further comprises a second portion including a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate comprising a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism. In this feature, the hole is positionable in registry with the well, and the at least one fastening assembly is further configured for removably fastening the second portion of the interface to the body of the watercraft. 
     In another feature, the first portion is a top portion and the first plate is a top plate, and wherein the second portion is a bottom portion and the second plate is a bottom plate. 
     In yet another feature, the channel is adapted for removably securing the propulsion mechanism to the interface. 
     In still another feature, the at least one fastening assembly is configured for removably fastening the first portion to the second portion of the interface. Preferably, the at least one fastening assembly includes a first segment engaging the first portion of the interface and a second segment engaging the second portion of the interface. The first and second segments of the at least one fastening assembly collaborate to force the first and second portions of the interface toward one another to sandwich the body of the watercraft between the first and second plates. 
     In a further feature, the first segment of the at least one fastening assembly comprises a threaded fastener engaging the first plate of the first portion and the second segment of the at least one fastening assembly comprises a fastening projection provided with a threaded hole, the threaded fastener being engageable in the threaded hole of the fastening projection to force the first and second portions of the interface toward one another. 
     In yet a further feature, the at least one fastening assembly is further configured for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the second plate. 
     In still a further feature, the at least one fastening assembly comprises four fastening assemblies. 
     In one feature, the interface further comprises at least one guiding assembly for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the second plate. Preferably, the at least one guiding assembly comprises a plurality of fins extending upwardly from the second plate of the second portion, about the periphery of the hole, the fins being configured for positioning the channel of the first portion in registry with the hole of the second portion as the first and second portions of the interface are forced toward one another. 
     In one feature, the fins extend from at least one of a ridge extending upwardly from the second plate of the second portion, a female portion of a guide assembly and the second segment of the second portion. 
     In another feature, the at least one guiding assembly comprises a guiding assembly mounted to the at least one fastening assembly. 
     In still another feature, the propulsion mechanism is a foot propulsion mechanism. 
     In yet another feature, the propulsion mechanism is an oscillating flapper propulsion mechanism. 
     In a further feature, the propulsion mechanism is a motorised propulsion mechanism. 
     In still a further feature, the watercraft is a kayak, and preferably a fishing kayak. 
     In another feature, the watercraft is a small boat. 
     In a further feature, the interface further comprises a lock mechanism for removably securing the propulsion mechanism to the interface. Preferably, the lock mechanism is mounted in the channel of the first portion of the interface. More preferably, the propulsion mechanism comprises a shaft including at least projection on one side of the propulsion mechanism, and the channel comprises at least one recess for slidably receiving therein the at least one shaft projection. The lock mechanism is positioned in the channel adjacent to the recess and being movable between a lock position and an unlock position, the lock mechanism in lock position engaging the shaft projection received in the recess to prevent vertical movement of the propulsion mechanism relative to the channel. 
     According to another broad aspect, there is provided a watercraft comprising: 
     rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, 
     an interface for mounting a propulsion mechanism to the body of the watercraft, the interface including: 
     a first portion including a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about the periphery of the well, and at least one channel extending from the first plate, the channel being positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; and 
     at least one fastening assembly for removably fastening the first portion to the body of the watercraft. 
     In one feature, the interface further comprises a second portion including a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate comprising a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism. In this feature, the hole is positionable in registry with the well, and the at least one fastening assembly is further configured for removably fastening the second portion of the interface to the body of the watercraft. 
     In another feature, the first portion is a top portion and the first plate is a top plate, and wherein the second portion is a bottom portion and the second plate is a bottom plate. 
     In yet another feature, the channel is adapted for removably securing the propulsion mechanism to the interface. 
     In still another feature, the at least one fastening assembly is configured for removably fastening the first portion to the second portion of the interface. Preferably, the at least one fastening assembly includes a first segment engaging the first portion of the interface and a second segment engaging the second portion of the interface. The first and second segments of the at least one fastening assembly collaborate to force the first and second portions of the interface toward one another to sandwich the body of the watercraft between the first and second plates. 
     In a further feature, the first segment of the at least one fastening assembly comprises a threaded fastener engaging the first plate of the first portion and the second segment of the at least one fastening assembly comprises a fastening projection provided with a threaded hole, the threaded fastener being engageable in the threaded hole of the fastening projection to force the first and second portions of the interface toward one another. 
     In yet a further feature, the at least one fastening assembly is further configured for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the second plate. 
     In still a further feature, the at least one fastening assembly comprises four fastening assemblies. 
     In one feature, the interface further comprises at least one guiding assembly for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the second plate. Preferably, the at least one guiding assembly comprises a plurality of fins extending upwardly from the second plate of the second portion, about the periphery of the hole, the fins being configured for positioning the channel of the first portion in registry with the hole of the second portion as the first and second portions of the interface are forced toward one another. 
     In one feature, the fins extend from at least one of a ridge extending upwardly from the second plate of the second portion, a female portion of a guide assembly and the second segment of the second portion. 
     In another feature, the at least one guiding assembly comprises a guiding assembly mounted to the at least one fastening assembly. 
     In still another feature, the propulsion mechanism is a foot propulsion mechanism. 
     In yet another feature, the propulsion mechanism is an oscillating flapper propulsion mechanism. 
     In a further feature, the propulsion mechanism is a motorised propulsion mechanism. 
     In still a further feature, the watercraft is a kayak, and preferably a fishing kayak. 
     In another feature, the watercraft is a small boat. 
     In a further feature, the interface further comprises a lock mechanism for removably securing the propulsion mechanism to the interface. Preferably, the lock mechanism is mounted in the channel of the first portion of the interface. More preferably, the propulsion mechanism comprises a shaft including at least projection on one side of the propulsion mechanism, and the channel comprises at least one recess for slidably receiving therein the at least one shaft projection. The lock mechanism is positioned in the channel adjacent to the recess and being movable between a lock position and an unlock position, the lock mechanism in lock position engaging the shaft projection received in the recess to prevent vertical movement of the propulsion mechanism relative to the channel. 
     According to another broad aspect, there is provided an interface for mounting a propulsion mechanism to a watercraft including a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion. In this broad aspect, the interface comprises: 
     a first portion including a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about the periphery of the well, and at least one channel extending from the first plate, the channel being positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; 
     a second portion including a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate comprising a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, the hole being positionable in registry with the well and with the channel of the first portion; 
     at least one fastening assembly for removably fastening the second portion to the first portion of the interface, the at least one fastening assembly including a first segment engaging the first portion of the interface and a second segment engaging the second portion of the interface, the first and second segments of the at least one fastening assembly collaborating to force the first and second portions of the interface toward one another to sandwich the body of the watercraft between the first and second plates; 
     at least one guiding assembly for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the first plate. 
     According to yet another broad aspect, there is provided a watercraft comprising: 
     rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, 
     an interface for mounting a propulsion mechanism to the body of the watercraft, the interface including: 
     a first portion including a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about the periphery of the well, and at least one channel extending from the first plate, the channel being positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; 
     a second portion including a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate comprising a hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, the hole being positionable in registry with the well and with the channel of the first portion; 
     at least one fastening assembly for removably fastening the second portion to the first portion of the interface, the at least one fastening assembly including a first segment engaging the first portion of the interface and a second segment engaging the second portion of the interface, the first and second segments of the at least one fastening assembly collaborating to force the first and second portions of the interface toward one another to sandwich the body of the watercraft between the first and second plates; 
     at least one guiding assembly for maintaining the channel of the first portion in registry with the hole of the second portion when the at least one fastening assembly is fastened and the channel is spaced-apart from the first plate. 
     In some aspects, a kayak includes a substantially rigid body having a deck side, a hull side, and a well extending through the deck side and the hull side; an interface for mounting a foot-driven propulsion mechanism to the substantially rigid body, the interface including: a first portion near to the hull side or the deck side, the first portion comprising a first hole for allowing passage of at least a portion of the foot-driven propulsion mechanism therethrough; a second portion near to the other of the hull side or the deck side on an opposite side of the well from the first portion, the second portion comprising a second hole for allowing passage of at least a portion of the foot-driven propulsion mechanism therethrough, wherein the second portion is a separate component from at least the first portion; and a channel structure disposed in the well between the first portion and the second portion, the channel structure being sized and shaped for allowing passage of a portion of the foot-driven propulsion mechanism therethrough and for removably securing the foot-driven propulsion mechanism to the interface. A distal end of the channel structure is securely coupled to the first portion and/or the second portion. 
     In some implementations, the channel structure is glued to the first portion and/or the second portion. The distal end of the channel structure securely mates with the first portion and/or the second portion via a projection and a corresponding recess. The distal end of the channel structure securely mates with the first portion and/or the second portion via multiple projections and corresponding recesses. The channel structure is integrally formed with, and extends away from, the first portion, and multiple projections and corresponding recesses mate with one another to couple the channel structure with the second portion. 
     In some implementations, the channel structure is glued to the second portion. The channel structure is plastic-welded to the first portion or second portion. In some implementations, the kayak further includes drainage holes in the interface through which water can drain. In some implementations, the interface further comprises at least one guide extending from the second portion to align the channel structure with the second hole of the second portion. 
     In some implementations, the at least one guide defines a lip for receiving a portion of the channel structure thereon. In some implementations, the lip extends at least partially around a periphery of the second hole of the second portion. In some implementations, the well structure includes a recess near the deck side and a recess near the hull side, wherein each of the first portion and the second portion are disposed within a respective recess at the hull side or the deck side. In some implementations, the interface further comprises at least one guide extending from the first portion to align the channel structure with the first hole of the first portion. 
     In some implementations, the interface and the substantially rigid body of the kayak are formed by different plastic molding processes. In some implementations, the kayak further includes drainage holes in the interface through which water can drain. In some implementations, the kayak further includes a fastener for coupling the interface to the kayak, wherein the fastener comprises either screws and corresponding holes or a snapfit. In some implementations, the interface is removably coupled to the kayak. 
     In another aspect, a kayak includes a substantially rigid body having a deck side, a hull side, and a well extending through the deck side and the hull side, wherein the well includes a recess near the deck side; an interface for mounting a foot-driven propulsion mechanism to the substantially rigid body, the interface including: a first portion disposed in the recess near to the deck side of the kayak; a channel structure extending from the first portion, the channel structure disposed in the well, wherein the channel structure is sized and shaped for receiving therein at least a portion of the foot-driven propulsion mechanism and for removably securing the foot-driven propulsion mechanism to the interface; and multiple screws securing the first portion to the kayak. 
     In some implementations, the channel structure is integrally formed with the first portion by different plastic molding processes than that used to form the kayak. In some implementations, the channel structure is a separate component from the first portion, wherein both the channel structure and the first portion are formed by different plastic molding processes than that used to form the kayak, and wherein the channel structure is glued to the first portion. 
     In another aspect, a kayak extending longitudinally between rear and front ends and transversely between left and right sides, the kayak includes a foot-driven propulsion mechanism including first and second shafts with first and second pedals, first and second flappers, and a core body between the first and second shafts and first and second flappers, the core body including first and second projections that include first and second ends. The kayak includes a body having a deck portion with a top side and a hull portion with a bottom side adapted to contact water. The top side includes a top peripheral wall section defining a top opening and the bottom side includes a bottom peripheral wall section defining a bottom opening. The kayak including an interface having top and bottom plates and a channel portion extending between the top and bottom plates. The top plate includes a top peripheral wall section defining a top opening adapted to at least partially receive the foot-driven propulsion mechanism and the bottom plate having a bottom peripheral wall section defining a bottom opening adapted to at least partially receive the foot-driven propulsion mechanism. The channel portion includes an internal peripheral wall defining a hollow space to at least partially receive the foot-driven propulsion mechanism. The internal peripheral wall of the interface includes first and second projections or recesses. The first and second ends of the first and second projections are mounted to the first and second projections or recesses. 
     In some implementations, the top peripheral wall section of the deck portion includes a top peripheral recess, the bottom peripheral wall section of the deck portion includes a bottom peripheral recess. The top peripheral wall of the interface is received in the top peripheral recess, and the bottom peripheral wall of the interface is received in the bottom peripheral recess. 
     In some implementations, the top peripheral wall of the interface is snap-fit or friction fit into the top peripheral recess and the bottom peripheral wall of the interface is snap-fit or friction fit into the bottom peripheral recess. In some implementations, the top peripheral wall of the interface is secured to the top peripheral recess with treaded fasteners or rivets and wherein the bottom peripheral wall of the interface is secured to the bottom peripheral recess with treaded fasteners or rivets. In some implementations, the top peripheral wall of the interface is glued or plastic welded to the top peripheral recess and the bottom peripheral wall of the interface is glued or plastic welded to the bottom peripheral recess. 
     In some implementations, the channel portion of the interface is integrally formed with the top plate or the bottom plate. In some implementations, the first and second projections are rear and front projections, the first and second projections or recesses are rear and front projections or recesses, the core body of the foot-driven propulsion mechanism includes left and right projections having left and right ends. The internal peripheral wall of the interface includes left and right projections or recesses, and the left and right ends of the left and right projections are mounted to the left and right projections or recesses. In some implementations, the channel portion of the interface includes first and second side walls, each of the first and second side walls includes a first recess, a second recess terminating into a lower funnel-shape slot, and a top funnel slot, The first recess has a shape to generally conform to a periphery of the core body of the foot propulsion mechanism, and the lower funnel-shaped slot is adapted to receive left and right transverse projections of the core body of the foot propulsion mechanism. In some implementations, the top funnel slot is adapted to at least partially receive the core body of the foot propulsion mechanism. In some implementations, the kayak includes a lock that is pivotable between an unlocked position and a locked position, in the locked position, movement of the foot propulsion mechanism is prevented. In some implementations, a top side of the top peripheral wall of the interface is generally flush with the top side of the deck portion at a joint between the top peripheral wall and the top side and a bottom side of the bottom peripheral wall of the interface is generally flush with the bottom side of the hull portion at a joint between the bottom peripheral wall and the bottom side. In some implementations, the body is made of a first plastic material having a first rigidity and the interface is made of a second plastic material having a second rigidity, the second rigidity being greater than the first rigidity. 
     In another aspect, a kayak extending longitudinally between rear and front ends and transversely between left and right sides, the kayak includes: a foot-driven propulsion mechanism having first and second shafts with first and second pedals, first and second flappers, and a core body between the first and second shafts and first and second flappers, the core body having rear and front projections that include rear and front ends. The kayak includes a body having a deck portion with a top side and a hull portion with a bottom side adapted to contact water. The top side includes a top peripheral wall section defining a top opening and the bottom side includes a bottom peripheral wall section defining a bottom opening; and an interface having top and bottom plates and a channel portion extending between the top and bottom plates. The top plate includes a top peripheral wall section defining a top opening adapted to at least partially receive the foot-driven propulsion mechanism and the bottom plate includes a bottom peripheral wall section defining a bottom opening adapted to at least partially receive the foot-driven propulsion mechanism. The channel portion includes an internal peripheral wall defining a hollow space to at least partially receive the foot-driven propulsion mechanism, the internal peripheral wall of the interface includes rear and front side walls, the rear side wall has a rear projection or recesses. The front side wall includes a front projection or recesses. The rear and front ends of the rear and front projections are mounted to the rear and front projections or recesses. 
     In some implementations, the top peripheral wall section of the deck portion comprises a top peripheral recess, wherein the bottom peripheral wall section of the deck portion comprises a bottom peripheral recess, wherein the top peripheral wall of the interface is received in the top peripheral recess, and wherein the bottom peripheral wall of the interface is received in the bottom peripheral recess. 
     In some implementations, the top peripheral wall of the interface is snap-fit or friction fit into the top peripheral recess and wherein the bottom peripheral wall of the interface is snap-fit or friction fit into the bottom peripheral recess. 
     In some implementations, the top peripheral wall of the interface is secured to the top peripheral recess with treaded fasteners or rivets and wherein the bottom peripheral wall of the interface is secured to the bottom peripheral recess with treaded fasteners or rivets. 
     In some implementations, the top peripheral wall of the interface is glued or plastic welded to the top peripheral recess and wherein the bottom peripheral wall of the interface is glued or plastic welded to the bottom peripheral recess. In some implementations, the channel portion of the interface is integrally formed with the top plate or the bottom plate. In some implementations, the core body of the foot-driven propulsion mechanism includes left and right projections having left and right ends. The internal peripheral wall of the interface includes left and right projections or recesses, and the left and right ends of the left and right projections are mounted to the left and right projections or recesses. 
     In some implementations, the channel portion of the interface includes first and second side walls. Each of the first and second side walls includes a first recess, a second recess terminating into a lower funnel-shape slot, and a top funnel slot. The first recess has a shape to generally conform to a periphery of the core body of the foot propulsion mechanism, and the lower funnel-shaped slot is adapted to receive left and right transverse projections of the core body of the foot propulsion mechanism. 
     In some implementations, the top funnel slot is adapted to at least partially receive the core body of the foot propulsion mechanism. In some implementations, the kayak includes a lock that is pivotable between an unlocked position and a locked position, wherein in the locked position, movement of the foot propulsion mechanism is prevented. In some implementations, a top side of the top peripheral wall of the interface is generally flush with the top side of the deck portion at a joint between the top peripheral wall and the top side and a bottom side of the bottom peripheral wall of the interface is generally flush with the bottom side of the hull portion at a joint between the bottom peripheral wall and the bottom side. In some implementations, the body is made of a first plastic material having a first rigidity and the interface is made of a second plastic material having a second rigidity, the second rigidity being greater than the first rigidity. 
     In another aspect, a kayak extending longitudinally between rear and front ends and transversely between left and right sides, the kayak includes a body having a deck portion with a top side and a hull portion with a bottom side adapted to contact water. The top side includes a top peripheral wall section defining a top opening and the bottom side includes a bottom peripheral wall section defining a bottom opening; and an interface having top and bottom plates and a channel portion extending between the top and bottom plates. The top plate includes a top peripheral wall section defining a top opening adapted to at least partially receive a foot-driven propulsion mechanism and the bottom plate comprising a bottom peripheral wall section defining a bottom opening adapted to at least partially receive the foot-driven propulsion mechanism. The channel portion includes an internal peripheral wall defining a hollow space to at least partially receive the foot-driven propulsion mechanism. The top peripheral wall section of the deck portion comprises a top peripheral recess, wherein the bottom peripheral wall section of the deck portion includes a bottom peripheral recess, the top peripheral wall of the interface is received in the top peripheral recess, and the bottom peripheral wall of the interface is received in the bottom peripheral recess. 
     In some implementations, the top peripheral wall of the interface is snap-fit or friction fit into the top peripheral recess and wherein the bottom peripheral wall of the interface is snap-fit or friction fit into the bottom peripheral recess. 
     In some implementations, the top peripheral wall of the interface is secured to the top peripheral recess with treaded fasteners or rivets and wherein the bottom peripheral wall of the interface is secured to the bottom peripheral recess with treaded fasteners or rivets. In some implementations, the top peripheral wall of the interface is glued or plastic welded to the top peripheral recess and the bottom peripheral wall of the interface is glued or plastic welded to the bottom peripheral recess. In some implementations, the channel portion of the interface is integrally formed with the top plate or the bottom plate. In some implementations, the foot-driven propulsion mechanism includes first and second shafts with first and second pedals, first and second flappers, and a core body between the first and second shafts and first and second flappers, the core body having rear and front projections comprising rear and front ends. The internal peripheral wall of the interface includes rear and front side walls, the rear side wall includes a rear projection or recesses. The front side wall includes a front projection or recesses, and the rear and front ends of the rear and front projections are mounted to the rear and front projections or recesses. 
     In some implementations, the core body of the foot-driven propulsion mechanism includes left and right projections having left and right ends, the internal peripheral wall of the interface includes left and right projections or recesses, and the left and right ends of the left and right projections are mounted to the left and right projections or recesses. In some implementations, the channel portion of the interface includes first and second side walls. Each of the first and second side walls includes a first recess, a second recess terminating into a lower funnel-shape slot, and a top funnel slot. The first recess has a shape to generally conform to a periphery of the core body of the foot propulsion mechanism, and the lower funnel-shaped slot is adapted to receive left and right transverse projections of the core body of the foot propulsion mechanism. 
     In some implementations, the top funnel slot is adapted to at least partially receive the core body of the foot propulsion mechanism. In some implementations, the kayak includes a lock that is pivotable between an unlock position and a lock position, wherein in the lock position, movement of the foot propulsion mechanism is prevented. In some implementations, a top side of the top peripheral wall of the interface is generally flush with the top side of the deck portion at a joint between the top peripheral wall and the top side and a bottom side of the bottom peripheral wall of the interface is generally flush with the bottom side of the hull portion at a joint between the bottom peripheral wall and the bottom side. In some implementations, the body is made of a first plastic material having a first rigidity and the interface is made of a second plastic material having a second rigidity, the second rigidity being greater than the first rigidity. 
     In some aspects, a watercraft includes a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, an interface for mounting a propulsion mechanism to the body of the watercraft, the interface including: a top plate, a first bottom plate spaced-apart from the first top plate and extending generally parallel thereto, and a first channel portion extending between the first top plate and the first bottom, generally transverse thereto, the first top plate abutting a first peripheral segment of the deck portion, the first bottom plate abutting a first peripheral segment of the hull portion and the first channel portion extending in the well when the first section is mounted to the rigid body. The watercraft includes a second interface section comprising a second top plate, a second bottom plate spaced-apart from the second top plate and extending generally parallel thereto, and a second channel portion extending between the second top plate and the second bottom, generally transverse thereto, the second top plate abutting a second peripheral segment of the deck portion, the second bottom plate abutting a second peripheral segment of the hull portion and the second channel portion extending in the well when the second interface section is mounted to the rigid body. The watercraft includes a fastening assembly for fastening the first and second interface sections either to one another or to the body of the watercraft. 
     In some implementations, the first interface section is a left interface section and the second interface section is a right interface section. The first interface section is a rear interface section and the second interface section is a front interface section. 
     In some aspects, a watercraft includes a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, an interface for mounting a propulsion mechanism to the rigid body of the watercraft, the interface including: a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about a periphery of the well, the first plate including a first hole, a channel receivable in the first hole and securable to the first plate, the channel being positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; a securing assembly for securing the channel to the first plate; and at least one fastening assembly for removably fastening the interface to the body of the watercraft. 
     In some implementations, the interface further includes a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate comprising a second hole sized and shaped for receiving therethrough a portion of the propulsion mechanism, the hole being positionable in registry with well and with the channel. The securing assembly is further configured for securing the channel to the second plate. The at least one fastening assembly is configured for removably fastening the first plate to the second plate of the interface. The at least one fastening assembly includes a first segment engaging the first plate of the interface and a second segment engaging the second plate of the interface, the first and second segments of the at least one fastening assembly collaborating to force the first and second plates of the interface toward one another to sandwich the rigid body of the watercraft therebetween. 
     In some aspects, a watercraft includes a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, an interface for mounting a propulsion mechanism to the rigid body of the watercraft, the interface including: a first plate positionable adjacent to one of the hull portion and the deck portion of the watercraft, about a periphery of the well, the first plate including a first hole, a second plate positionable adjacent to the other of the hull portion and the deck portion of the watercraft, about the periphery of the well, the second plate including a second hole, a channel receivable in the first hole and securable to the first plate, the channel being positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface, the channel being further positionable in registry with the second hole of the second plate; a securing assembly for securing the channel to the first plate; and at least one fastening assembly for removably fastening the interface to the body of the watercraft. 
     In some implementations, the securing assembly is further configured for securing the channel to the second plate. The at least one fastening assembly is configured for removably fastening the first plate to the second plate of the interface. The at least one fastening assembly includes a first segment engaging the first plate of the interface and a second segment engaging the second plate of the interface, the first and second segments of the at least one fastening assembly collaborating to force the first and second plates of the interface toward one another to sandwich the rigid body of the watercraft therebetween. 
     In some aspects, a propulsion mechanism for a watercraft including a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, the propulsion mechanism includes a core support; an interface comprising a channel secured to the core support and a securing assembly for removably mounting the channel to the body of the watercraft, the channel being positionable in the well; and a propeller mounted to the core support, the propeller being configured to extend below the hull portion of the watercraft when the propulsion mechanism is mounted to the body of the watercraft. 
     In some implementations, the channel includes a top end and a bottom end, and wherein the interface further comprises a first plate mounted to one of the top end and the bottom end of the channel, the first plate abutting against the body when the propulsion mechanism is mounted to the body of the watercraft. The first plate of the interface is mounted to the top end the channel, the first plate abutting the deck portion of the body watercraft when the propulsion mechanism is mounted to the body of the watercraft. The first plate is mounted to the bottom end the channel, to first plate abutting the hull portion of the body watercraft when the propulsion mechanism is mounted to the body of the watercraft. 
     In some implementations, the propulsion mechanism further includes a set of left and right pedals operatively coupled to the propeller, the left and right pedals extending above the deck portion of the watercraft when the propulsion mechanism is mounted to the body of the watercraft. In some implementations, the propeller includes a pair of oscillating, flexible flappers. In some implementations, the set of left and right pedals the pair of is operatively coupled to the flexible flappers via one a cable transmission and a chain transmission. 
     In some aspects, a method for manufacturing a watercraft including a rigid body having a deck portion, a hull portion and an embedded propeller interface extending between the deck portion and the hull portion by thermoforming, the method includes providing a mold including a deck shell and a hull shell, the deck shell and hull shell being movable relative to one another between an open position and a closed position; providing a propeller interface including a deck end and a hull end, the propeller interface being made of a first plastic material; providing first and second sheets of a second, thermoformable plastic material; moving the deck shell and the hull shell in the open position; positioning the first sheet of the second, thermoformable plastic material adjacent to one of the deck portion and the hull portion; positioning the second sheet of the second thermoformable plastic material adjacent to the other of the deck portion and the hull portion; positioning the propeller interface between the first and second sheets of the second, thermoformable material; moving the deck shell and the hull shell of the mold in the closed position; simultaneously thermoforming the deck portion and the hull portion to obtain the rigid body; moving the deck shell and the hull shell of the mold in the open position. A watercraft manufactured according to the above described method. 
     In some aspects, a watercraft includes a rigid body having a deck portion, a hull portion and a well extending between the deck portion and the hull portion, an interface for mounting a propulsion mechanism to the body of the watercraft, the interface including: positionable in the well, the channel being sized and shaped for receiving therein a portion of the propulsion mechanism and for mounting the propulsion mechanism to the interface; a securing assembly for securing the channel to at least one of the deck portion and the hull portion. 
     In some aspects, a watercraft having a rigid body that includes a deck portion, a hull portion with a keel portion, and a well extending between the deck portion and the keel portion, the watercraft includes an interface for mounting a pedal operated propulsion mechanism to the rigid body of the watercraft, the interface includes a channel portion configured to fit within the well, and configured to removably receive the pedal operated propulsion mechanism. 
     In some implementations, the interface further includes a top plate having a hole therein, the top plate abutting the deck portion at least partially around the well. The interface further includes a bottom plate having a hole therein, the bottom plate abutting the keel portion at least partially around the well. The watercraft further includes a fastening assembly for fastening the interface sections to the body of the watercraft. The fastening assembly includes one or more screws for fastening the top plate to the interface or the bottom plate to the interface. The pedal operated propulsion mechanism includes two pins, each extending from one side thereof, and the channel portion comprises recesses for receiving and supporting the pins and a lock that locks at least one of the pins in place. The channel portion is integrally formed with the top plate. The channel portion is integrally formed with the bottom plate. The channel portion extends only partially through the well. The channel portion extends only partially through the well at a middle portion of the well between the deck portion and the keel portion. The channel portion is force fit into the well. The channel portion is snap fit into the well. The top or bottom plate is force- or snap-fit to the hull. The hull is a thermo-molded material and the interface is an injection molded material. 
     In some aspects, a watercraft, includes a rigid body that includes a deck, a hull with a keel, and a well extending between the deck and the keel; an interface for mounting a pedal operated propulsion mechanism to the rigid body of the watercraft, the interface including at least two brackets configured to at least partially fit within the well, the at least two brackets configured to removably mount a pedal operated propulsion mechanism to the rigid body of the watercraft. 
     In some implementations, the at least two brackets comprise three brackets evenly spaced around the well. The at least two brackets comprise four brackets evenly spaced around the well. The four brackets include a forward bracket a rear bracket, and two side brackets. The forward bracket is configured to support a front of the pedal operated propulsion mechanism, the rear bracket is configured to support the rear of the pedal operated propulsion system, and the two side brackets are configured to support the sides of the pedal operated propulsion system. The pedal operated propulsion mechanism includes two pins, each extending from one side thereof, and each of the side brackets comprises a recess for receiving and supporting a respective pin of the two pins, and a lock that locks at least one of the pins in place. The brackets are affixed to the well. The brackets are affixed to a lip formed in the well. 
     In some implementations, the watercraft further includes a top plate with a hole therein through which at least a portion of the pedal powered propulsion system can pass, where the top plate abuts the deck. The top plate is affixed to the deck using screws, rivets, glue, or plastic-welding. The watercraft further includes a bottom plate with a hole therein through which at least a portion of the pedal powered propulsion system can pass, where the bottom plate abuts the hull at or near the keel. The bottom plate is affixed to the deck using screws, rivets, glue, or plastic-welding. The bottom plate is affixed to the deck using screws, rivets, glue, or plastic-welding. The hull is made from a thermo-molded material and the interface is made from an injection molded material. 
     In some aspects, a method of making a rigid watercraft, including injection molding an interface configured to removably receive and mount a pedal operated propulsion mechanism to the rigid watercraft; thermo-molding a body that includes a deck, a hull with a keel, and the well extending between the deck and the keel; affixing the interface to the body. 
     In some implementations, the method further includes, after the thermo-molding, and while the body is still warm, inserting the interface at least partially into the well, and allowing the body to shrink about the interface. The injection molding forms the interface including: (i) a channel configured to fit within the well formed in the hull of the watercraft, (ii) the channel and a top plate that is configured to abut the deck, (iii) the channel and a bottom plate configured to abut the keel, or (iv) the channel the top plate and the bottom plate. The injection molding integrally forms the channel with either or both of the top and bottom plates. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Having thus generally described the nature of the invention, reference will now be made to the accompanying drawings, showing by way of illustration example embodiments thereof and in which: 
         FIG.  1    is a top, rear right perspective view of a kayak in accordance with some embodiments; 
         FIG.  2    is a bottom, rear right perspective view of the kayak shown in  FIG.  1   ; 
         FIG.  3    is a top, front right perspective view of the kayak shown in  FIG.  1   ; 
         FIG.  4    is a top plan view of the kayak shown in  FIG.  1   ; 
         FIG.  5    is a left elevation view of the kayak shown in  FIG.  1   ; 
         FIG.  6    is a rear elevation view of the kayak shown in  FIG.  1   ; 
         FIG.  7    is a bottom plan view of the kayak shown in  FIG.  1   ; 
         FIG.  8    is an enlarged, top front right perspective view of a body of the kayak shown in  FIG.  1   , in accordance with some embodiments; 
         FIG.  9    is an enlarged, bottom front right perspective view of the body shown in  FIG.  8   ; 
         FIG.  10    is a cross-section view of the body shown in  FIG.  8   , taken along line X-X; 
         FIG.  11    is a top, front right perspective view of an interface and a propulsion mechanism mounted thereto of the kayak shown in  FIG.  1   , in accordance with one embodiment. 
         FIG.  12    a bottom, rear right perspective view of the interface and propulsion mechanism shown in  FIG.  11   ; 
         FIG.  13    is a top, rear right perspective view of the interface shown in  FIG.  11   ; 
         FIG.  14    is a cross-sectioned perspective view of the interface shown in  FIG.  13   , taken along line XIV-XIV; 
         FIG.  15    is an exploded view of the interface shown in  FIG.  13   ; 
         FIG.  16 A  is a bottom, rear right perspective view of a bottom portion of the interface shown in  FIG.  13   , in accordance with one embodiment; 
         FIG.  16 B  is a partial, enlarged view of the bottom portion of the interface shown in  FIG.  16 A , for better showing a fastening projection; 
         FIG.  16 C  is another partial, enlarged view of the bottom portion of the interface shown in  FIG.  16 A , for better showing a female portion of a directing assembly; 
         FIG.  17    is a top plan view of the bottom portion shown in  FIG.  16 A ; 
         FIG.  18    is a right elevation view of the bottom portion shown in  FIG.  16 A ; 
         FIG.  19    is a rear elevation view of the bottom portion shown in  FIG.  16 A ; 
         FIG.  20    is a bottom plan view of the bottom portion shown in  FIG.  16 A ; 
         FIG.  21    is a rear, top right perspective view of a top portion of the interface shown in  FIG.  13   , in accordance with one embodiment; 
         FIG.  22    is a rear, bottom right perspective view of the top portion shown in  FIG.  21   ; 
         FIG.  23    is a to plan view of the top portion shown in  FIG.  21   ; 
         FIG.  24    is a rear elevation view of the top portion shown in  FIG.  21   ; 
         FIG.  25    is a right elevation view of the top portion shown in  FIG.  21   ; 
         FIG.  26    is a bottom plan view of the top portion shown in  FIG.  21   ; 
         FIG.  27    is a rear, top right perspective view of the propulsion mechanism shown in  FIG.  13   ; 
         FIG.  28    is an enlarged right elevation view of the propulsion mechanism shown in  FIG.  27   ; 
         FIG.  29    is a rear, top right perspective view of a core support of the propulsion mechanism shown in  FIG.  27   , with a pedal shaft mounted thereto; 
         FIG.  30    is a rear, bottom right perspective view of the core support shown in  FIG.  29   , without the pedal shaft; and 
         FIG.  31    is a rear, top right, partially exploded view of the kayak shown in  FIG.  1   . 
         FIG.  32    is a top perspective view of an interface, in accordance with some embodiments. 
         FIG.  33    is a top view of the interface shown in  FIG.  32    bottom, rear right perspective view of the interface and propulsion mechanism shown in  FIG.  32   ; 
         FIG.  34    is a top, perspective view of a left portion of the interface shown in  FIG.  11   ; 
         FIG.  35    is a schematic representation of an interface according to another embodiment; 
         FIG.  36 A  is a top perspective view of the interface represented in  FIG.  35    in accordance with some embodiments; 
         FIG.  36 B  is a top perspective view of the interface represented in  FIG.  35   , in accordance with an alternate embodiment; 
         FIG.  37    is a schematic representation of an interface in accordance to an embodiment; 
         FIG.  38    is a top perspective view of the interface represented in  FIG.  337   ; 
         FIG.  39    is a schematic representation of an interface, in accordance with some embodiments; 
         FIG.  40    is a schematic representation of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  41    is a perspective view of the interface and propulsion mechanism represented in  FIG.  40   , in accordance with some embodiments; 
         FIG.  42    is a perspective view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  43    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  44    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  45    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  46    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  47    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  48    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments; 
         FIG.  49    is a cross-section view of an interface and propulsion mechanism, in accordance with some embodiments. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS.  1  to  7    show an example of a watercraft in accordance with an embodiment of the invention. In this embodiment, the watercraft is a fishing kayak  10  comprising a body  12  having a bow end  14  and a stern end  16  opposite the bow end  14 . The body  12  extends along a longitudinal axis L 1 -L 1  from the bow end  14  to the stern end  16 . The kayak  10  has a length L defined by the longitudinal axis L 1 -L 1 , a width W transversal to the longitudinal axis L 1 -L 1 , and a height H transversal to the widthwise and longitudinal directions. As the kayak  10  is primarily designed for fishing, the body  12  of the kayak  10  may be made relatively wide to assist in providing increased stability to the watercraft. 
     The body  12  of the kayak  10  comprises a deck  20  defining a top side  22  of the body  12  and a hull  24  defining a bottom side  26  of the body  12  (best shown in  FIG.  5   ). The deck  20  is configured for accommodating a user of the kayak  10  while the hull  24  is configured to engage water onto which the kayak  10  floats and travels. 
     In the illustrated embodiment, the deck  20  is provided with various features that can be useful to the user. For example, in the embodiment depicted, a seat  28  is disposed atop the deck  20  for allowing a user of the fishing kayak  10  to sit in a generally upright position. The seat  28  comprises a seat bottom  30  and a backrest  32 . The deck  20  also comprises a leg area  34  located forwardly of the seat  28  for supporting the user&#39;s legs and feet. In this embodiment, the leg area  34  comprises a generally oblong well  100  (best shown in  FIGS.  9  to  10   ) defined in the body  12 , an interface  300  mounted in the well  100  and a foot propulsion mechanism  500  mounted to the interface  300 , for allowing a user seating on the seat  28  to propel the kayak  10 , as it will be described in greater details below. The leg area  34  may also be used for the user to stand while fishing. It will be understood that such features may not necessarily be found in conventional (i.e., recreational/non-fishing) kayaks, or that such features may be configured differently without departing from the scope of this embodiment. 
     In this embodiment, the deck  20  also comprises a covered storage compartment  36  adjacent the bow end  14  of the body  12  and an open storage compartment  38  located between the covered storage compartment  36  and the leg area  34 . 
     The deck  20  also comprises covered storage compartment  40  adjacent the stern end  16  of the body  12 , as well as an open storage compartment  42  located between the covered storage compartment  40  and the seat  28 . As it will be appreciated, open storage compartments  36 ,  38 ,  40  and  42  may be useful to store equipment and, in the case of the covered storage compartments  36  and  40 , to protect such equipment from exposure to water. The open storage compartments  38 ,  42  may comprise securing cords  44 ,  46  (such as for example bungee cords) to secure equipment in the open storage compartments  38 ,  42 . As an example, a cooler or other equipment and/or provisions useful for fishing may be secured in the open storage compartments  38 ,  42 . 
     At the stern end  16  of the deck  20 , the kayak  10  is provided with a rudder assembly  50 . The rudder assembly  50  is operatively coupled to a steering mechanism  52  located beside the seat  28  (in the illustrated embodiment, on the left side of the seat  28 ) via a cable transmission (not shown), for steering the kayak  10 . Furthermore, in the embodiment depicted, the deck  20  comprises three pole holders  56 ,  58  and  60  for holding fishing poles (not shown). The deck  20  also comprises a pair of paddle parks  62 ,  64  on each side of the seat  28  to securely hold paddles (not shown) generally parallel to the longitudinal axis L 1 -L 1  of the kayak  10 . 
     With reference to  FIGS.  1 ,  2  and  7   , the body  12  of the kayak  10  is also shown as comprising a pair of drainage holes  66 ,  68  through which water from the deck  20  may travel to the bottom side  26  of the body  12  and into a body of water on which the kayak  10  travels. 
     Defined in the leg area  34  of the body  12  and extending between the deck  20  and the hull  24 , is the generally oblong well configured for receiving therein the interface  300  for mounting a foot operated propulsion mechanism  500 . 
     With reference to  FIGS.  8  to  10   , the well  100  comprises first, second, third, fourth and fifth portions  102 ,  104 ,  106 ,  108  and  110 , respectively which sequentially extend from the deck  20  to the hull  24 . The first portion  102  comprises a peripheral wall  112  and a first abutment wall  114  extending perpendicular thereto. Together, the peripheral wall  112  and the first abutment wall  114  define a recess  116  sized and shaped for receiving therein a portion of the interface  300 , as it will become apparent below. Defined in the first abutment wall  114  are four holes  118   a - 118   d  for receiving therein threaded fasteners  120   a - 120   d  (shown in  FIG.  31   ), for securing a portion of the interface  300  to the body  12  of the kayak  10 , as it will become apparent below. The second portion  104  of the well  100  is located below the first portion  102 . The second portion  104  comprises a peripheral wall  122  having a top end  124  connected to the first abutment wall  114  of the first portion  102 , the top end  124  being curved to transition toward a lower end  126  which, extends at an angle of approximately 80 degrees relative to the horizontal. The lower end  126  of the peripheral wall  122  is connected to a second abutment wall  128 . The second abutment wall  128  extends generally horizontal, and comprises a plurality of holes  130   a - 130   d  for receiving therethrough a corresponding plurality of threaded fasteners  132   a - 132   d  (shown in  FIG.  31   ) for securing portion of the interface  300  to the body  12  of the kayak  10 , as it will become apparent below. Together, the peripheral wall  122  and the second abutment wall  128  define a second recess  134  for receiving a portion of the interface  300 , as it will become apparent below. 
     The third portion  106  of the well  100  also includes a peripheral wall  136  extending downwardly, as well as a lip  138  extending generally transverse to the peripheral wall  136 . The peripheral wall  136  and the lip  138  correspond to the junction between the deck portion  44  of the body  12  and the hull  24 , where they are welded of fused together during the manufacturing process. 
     Likewise, and referring to  FIGS.  9  and  10   , the fourth portion  108  of the well  100  includes a peripheral wall  140 , as well as an abutment wall  142  extending generally horizontal. Defined on the abutment wall  142  is an oblong channel  144  adjacent to the lip  138 , and four recesses  146   a - 146   b  for receiving therein portion of the interface  300 , as it will become apparent below. 
     Lastly, and referring to  FIG.  9   , the fifth portion  110  comprises a peripheral wall  148  and an abutment wall  150 . Together, the peripheral wall  148  and the abutment wall  150  define a recess  152  for receiving therein a portion of the interface  300 , as it will become apparent below. 
     Tuning now to  FIGS.  11  to  26   , the interface  300  will now be described. The interface  300  comprises a bottom portion  302  and a top portion  304  configured to collaborate with the bottom section  302  to conceal the well  100  of the body  12  regardless of any manufacturing variations which may affect the thickness of the body  12  in this location, and to operatively accommodate the foot propulsion mechanism  500 . 
     With reference to  FIGS.  16 A to  20   , the bottom portion  302  comprises a plate  306  having a top face  308  and a bottom face  310 , the bottom plate  302  being sized and shape to fit in the recess  152  defined by the fifth portion  110  of well  100  defined in the body  12  of the kayak  10 . Defined at the center of the bottom plate  306  is an elongated hole  312  sized and shaped for allowing the passage of a portion of the propulsion mechanism  500 , the elongated hole  312  being surrounded by an inner peripheral wall  314  extending upwardly from the top face  308 . Also extending upwardly from the top face  308  of the plate  306  is a generally vertical outer peripheral wall  316 , located on the periphery of the plate  306 , as well as a plurality of reinforcement ridges  318 ,  320 ,  322  connecting the inner and outer peripheral walls  314 ,  316  (only some of the reinforcement ridges being identified with reference numerals  318 ,  320  and  322 ) Together with the inner and outer peripheral walls  314 ,  316 , the reinforcement ridges  318 ,  320 ,  322  contribute to provide the plate  306  with additional rigidity to torsion and/or bending. 
     Four snap hooks or snapfits  324   a - 324   d  also extend vertically from the top face  308  of the plate  306 . The snapfits  324   a - 324   d  are located proximal to the inner peripheral wall  314  and the elongated hole  312 , and each comprises a vertical base  326   a - 326   d  and a hook portion  328   a - 328   d . When the bottom portion  302  of the interface  300  is properly positioned in the oblong well  100  of the body  12 , the plate  306  is received in the recess  152  defined by the peripheral and abutment walls  148 ,  150  of the fifth portion  110 , and the snapfits  324   a - 324   d  extend to engage the lip  138  of the third portion  106 . As such, the snapfits  324   a - 324   d  contribute to maintain the position of the bottom portion  302  of the interface  300  in position relative to the body  12  of the kayak  10 . As it will be appreciated, the base and the hook portions  326   a - 326   d ,  328   a - 328   d  of the snapfits  324   a - 324   d  are sized to correspond to the distance between the abutment wall  150  of the fifth portion  110  and the top face of the lip  138 . Provided at the base of each snapfit  324   a - 324   d  is a draining hole  330   a - 330   d  for allowing water to evacuate the interface  300  (best shown in  FIG.  16 A ). 
     Also extending upwardly from the top face  308  of the bottom plate  306  are a plurality of fastening projections  332   a - 332   d , a plurality of female portions  334   a - 334   d  of a guide assembly  336 , as well as a plurality of guiding fins  338   a - 338   d . The fastening projections  332   a - 332   d  are located proximal to front and rear ends  340 ,  342  of the hole  312 , generally halfway between the inner and outer peripheral wall  314 ,  316 . With reference to  FIG.  16 B , each fastening projection  332   a - 332   d  comprises a cylindrical body  344  extending vertically, and a plurality of generally triangular reinforcement members  346 ,  348 ,  350  and  352  extending radially from the cylindrical body  344  (only fastening projection  332   d  being illustrated in  FIG.  16 B ). Each fastening projection  332   a - 332   d  also includes a fin  354  extending from one of the triangular reinforcement member  346  toward the inner peripheral wall  314 . Each fin  354  comprises a vertical edge  356 , extending generally vertical in a location slightly remote from the inner peripheral wall  314  of the bottom plate  306 , an inclined edge  358 , extending from a top end  360  of the vertical edge  356 , and a top edge  362  extending from a top end  364  of the inclined edge  358  toward the cylindrical body  344 . Defined in the cylindrical body  344  is a threaded bore  366 , for receiving therein a corresponding threaded fastener  132   a  to secure the bottom and top portions  302 ,  304  of the interface  300  with the body  12  of the kayak  10 , as it will become apparent below. 
     The female portions  334   a - 334   d  of the guide assembly  336  are located adjacent to the elongated hole  312 , on the front and rear sides of left and right indentations  368 ,  370  of the hole  312 . With reference to  FIG.  16 C , each female portion  334   a - 334   d  of the guide assembly  336  comprises a cylindrical body  372 , as well as a triangular reinforcement member  374  and a fin  376 , the reinforcement member  374  and the fins  376  extending radially from the cylindrical body  372 , in opposed directions (only female portion  334   a  being illustrated in  FIG.  16 C ). More specifically, the fin  376  extends between the cylindrical body  372  and the inner wall  314  of the plate  306 , while the triangular reinforcement member  374  extends toward the outer peripheral wall  316 . Each fin  376  comprises a vertical edge,  378  extending generally vertical in a location slightly remote from the inner peripheral wall  314  of the bottom plate  306 , as well as an inclined edge  380 , extending from a top end  382  of the vertical edge  378 , toward the cylindrical body  372 . As such, the inclined edges  380  of the fins  376  are inclined downwardly, toward the elongated hole  312  of the bottom portion  302 . Defined in the cylindrical body  372  of each female portion  334   a - 334   d  is a cylindrical hole  384  with a funneled opening  386  for receiving therein a male portion  390   a - 390   d  of the guide assembly  336 , as it will be described in greater detail below. 
     Returning to  FIG.  16 B , the guiding fins  338   a - 338   d  each comprises a vertical edge  392 , extending generally vertical in a location slightly remote from the inner peripheral wall  314  of the bottom plate  306 , an inclined edge  394 , extending from a top end  396  of the vertical edge  392 , a top edge  398  extending from a top end  397  of the inclined edge  394  toward the outer peripheral wall  316 , and a rear edge  399 , extending from the top edge  398 , at a slight angle, and connecting the same to a corresponding ridge  322 . As best shown in  FIG.  16 A , one guiding fin (e.g.  338   a ) is positioned generally halfway between the fin of a fastening portion (e.g. fin  354   a  of fastening portion  332   a ) and the fins of the female portion of the directing assembly  336  (e.g. fin  376  of female portion  334   a ). Together, the guiding fins  334   a - 334   d , the fins  354  of the fastening portions  332   a - 332   d  and the fins  376  of the female portions  334   a - 334   d  of the directing assembly  336  collaborate to guide the positioning of the top portion  304  of the interface  300  relative to the bottom portion  302  during the assembly of the interface  300 , and maintaining such position once the interface  300  is assembled, as it will become apparent below. While in the illustrated embodiment the interface  300  comprises four guiding fins  338   a - 338   d , four fins  354   a - 354   d  of fastening portions  332   a - 332   d  and four fins  376  of female portions  334   a - 334   d , it will be appreciated that the interface  300  could comprise a different number of fins, and that the configuration of the fins could vary. For instance, the interface could be provided with only four fins, whether they are found on the fastening portions  332   a - 332   d , the female portions  334   a - 334   d  or in any other suitable location of the bottom portion  302  of the interface. 
     With reference to  FIGS.  21  to  26   , the top portion  304  of the interface  300  will now be described. The top portion  304  comprises a generally horizontal top plate  400  as well as a channel  402  extending downwardly from the top plate  400 , for receiving and mounting therein the foot propulsion mechanism  500 . 
     The top plate  400  comprises a top face  404  and a bottom face  406 , and is sized and shaped to be received in the recess  116  defined by the first portion  102  of the oblong well  100  defined in the body  12  of the kayak  10 . Extending downwardly from the bottom face  406  of the top plate  400 , about it periphery, is an outer peripheral wall  408 . Also extending downwardly from the bottom face  406 , between the peripheral wall  408  and the channel  402 , are a plurality of reinforcement ridges  410 . Together with the outer peripheral wall  408  of the top plate  400 , the reinforcement ridges  410  contribute to provide the top plate  400  with additional rigidity in torsion and/or bending. 
     Defined on the top face  404  of the top plate  400 , about the periphery, are four peripheral recesses  412   a - 412   d  each comprising an oblong hole  414   a - 414   d . The oblong holes  414   a - 414   d  and the recesses  412   a - 412   d  are configured for receiving therein the threaded fasteners  120   a - 120   d  to fasten the top portion  304  of the interface  300  to the body  12  of the kayak  10 , and accommodating the head of such threaded fasteners  120   a - 120   d  when the interface  300  is properly fastened to the body  12 . Also defined on the top face  404  are four recesses  416   a - 416   d , which are positioned adjacent to the channel  402 . Each recess  416   a - 416   d  is provided with a corresponding hole  418   a - 418   d . As it will become apparent below, the holes  418   a - 418   d  are configured for allowing the passage of the threaded fasteners  132   a - 132   d  used to secure the top portion  304  of the interface  300  to the bottom portion  302  while the recesses  416   a - 416   d  are configured for accommodation the head of threaded fasteners  132   a - 132   d  when such bottom and top portion  302 ,  304  are secured together to the body  12  of the kayak  10 . 
     The channel  402  of the top portion  304  comprises an inner face  420  and an outer face  422 , and a bottom end  403 . At front and rear ends  424 ,  426  thereof, the channel  402  is provided with front and rear slots  428 ,  430  sized and shaped for respectively receiving front and rear ends  550 ,  552  of a core support  514  of the foot propulsion mechanism  500 . At the bottom of the front and rear slots  428 ,  430  are abutments  432 ,  434 , on which resting surfaces  554 ,  556  of the front and rear ends  550 , 552  of the core support  514  rest when the propulsion mechanism  500  is properly mounted to the interface  300 . 
     With reference to  FIG.  14   , the channel  402  also comprises a first V-shaped recess  440 , a second V-shaped recess  442  terminating into a lower funnel-shape slot  444 , as well as a top funnel slot  446  and a lock receiving recess  448 . At the bottom end  403  of the channel  402 , the first V-shaped recess  440  and the remainder of the channel  402  are sized and shaped to generally conform to the periphery of the core support  514  of the foot propulsion mechanism  500 , while the lower funnel-shaped slot  444  is configured to receive left and right transverse projections  548   a ,  548   b  of the core support  514 , as it will be described in greater details below. 
     The top funnel slot  446  is configured for receiving therein a mounting shaft  524  of the foot propulsion mechanism  500 . Mounted in each of the lock receiving recesses  448  is a lock  450 . In the illustrated embodiment, the lock  450  comprises a generally elongated flat member  452  including a convex lower end  454  and a concave upper end  456 , the concave upper end  456  being provided with grip elements  458  for enhancing contact between a finger of a user and the lock  450  for releasing the foot propulsion mechanism  500  from the interface  300 . Provided in an intermediate location between the upper end  456  and the lower end  454  is a hole (not shown) for receiving a fastener  460  for pivotably mounting the lock  450  in the lock receiving recess  448  of the channel  402 . When properly assembled, the lock  450  is pivotable between an unlock position for allowing the passage of the shaft (shown in dotted line in  FIG.  14   ) and a lock position for preventing the passage of the mounting shaft  524  of the foot propulsion mechanism (shown in continuous line in  FIG.  14   ) to thereby prevent unwanted removal of the foot propulsion mechanism  500  from the interface  300 . In one embodiment, the lock  450  is provided with a bias mechanism (not shown), for instance a coil spring or a torsion spring, to bias the lock  450  toward the lock position. 
     Returning to  FIGS.  22  to  25   , extending downwardly from the bottom face  406  of the top plate  400  are fastening projections  462   a - 462 , as well the male portions  390   a - 390   d  of the directing assembly  336 . Each fastening projection comprises a generally cylindrical body  466   a - 466   d  provided and a plurality of reinforcement members  468   a - 468   d ,  470   a - 470   d ,  472   a - 472   d  and  474   a - 474   d . Defined in the cylindrical body  466   a - 466   d  are holes  418   a - 418   d.    
     While in the above embodiment the guiding assembly (i.e. the guiding fins  334   a - 334   d , the fins  354  of the fastening portions  332   a - 332   d  and the fins  376  of the female portions  334   a - 334   d  of the directing assembly  336 ) are provided on the bottom plate  302  of the interface  300 , and the channel  402  is provided on the top portion  304  of the interface, it will be understood that the location of these components could be inverted, where the channel (e.g. channel  402 ) would be provided on the bottom portion  302  and the guiding assembly would be provided on the top portion  304  of the interface. 
     Turning now to  FIGS.  27  to  30   , the foot propulsion mechanism  500  will now be described. In the illustrated embodiment, the foot propulsion mechanism  500  is an oscillating flapper propulsion system and comprises a set of left and right pedals  502   a  and  502   b  extending upwardly from the top portion  304  of the interface  300  when the foot propulsion mechanism  500  is properly mounted thereto. The pedals  502   a ,  502   b  are operatively mounted to a pair of oscillating, flexible flappers  542   a ,  542   b  via a cable and chain transmission  540  supported on a core support  514 . 
     More specifically, the pedals  502   a ,  502   b  are adapted to be alternatively pushed by the user&#39;s feet to actuate the foot propulsion mechanism  500 . Each of the left and right pedals  502   a ,  502   b  comprises a shaft  506   a ,  506   b  including a lower end  508   a ,  508   b  and an upper end  510   a ,  510   b , as well as a footrest  512   a ,  512   b  for receiving one corresponding foot a the user. The lower ends  508   a , 508   b  of the shafts  506   a ,  506   b  are mounted to the core support  514 , which is configured to extend longitudinally (i.e. along the longitudinal axis L 1 -L 1  of the kayak  10  when the propulsion mechanism  500  is mounted to the interface  300 ), via a pair of mounting brackets  518   a ,  518   b . Each mounting bracket  518   a ,  518   b  allow adjustment of the distance between the footrests  512   a ,  512   b  and the seat  28  by way of an adjustment bolt  520  engaging the lower ends  508   a ,  508   b  of the shafts  506   a ,  506   b  and a plurality of adjustment holes  522  disposed on the mounting brackets  518   a ,  518   b . The mounting brackets  518   a ,  518   b  are also configured for receiving a mounting shaft  524  extending transverse to the longitudinal axis L 1 -L 1  and engaging the core support  514 . The mounting shaft  524  allow rotation of the left and right pedals  502   a , 502   b  relative to the core support  514 , about a rotation axis R 1 -R 1 . 
     With reference to  FIGS.  29  and  30   , the core support  514  is a monolithic piece and comprises a generally horizontal base  526  having a front end  528 , a rear end  530 , a top face  532  and a bottom face  534 . The generally horizontal base  526  is sized and shaped to be received in the channel  402  of the interface  300  and to substantially conceal the same when the foot propulsion mechanism  500  is mounted to the interface  300 , and comprises a plurality of indentations  536   a ,  536   b    538   a ,  538   b  for allowing the passage of the cable and chain transmission  540  operatively coupling the pedals  502   a ,  502   b  to the flappers  542   a ,  542   b . The core support  514  also comprise an upright mounting support  544  extending upwardly from the top face  532  of the horizontal base  526 , as well as three mounting brackets  546   a - 546   c  extending downwardly from the bottom face  534  for mounting the flappers  542   a ,  542   b . At the junction of the horizontal base  526  and the upright support  544 , generally halfway between the front and rear ends  528 ,  530 , are left and right transverse projections  548   a ,  548   b , which protrude on each side of the horizontal base  526 . As is will be described in greater details below, the left and right transverse projections  548   a ,  548   b  are sized and shaped to engage the lower funnel-shaped slot  444  of the interface  300 . 
     The upright mounting support  544  comprises a front end  550  and a rear end  552 . The front and rear ends  550 ,  552  of the upright mounding core support  514  extend beyond the front and rear ends  528 ,  530  of the horizontal base  526 , to define restring surfaces  554 ,  556  for mounting the foot propulsion mechanism  500  to the interface  300 , as it will become apparent below. The upright support  544  also comprises a pair of pulley mounting brackets  558   a ,  558   b  as well as a transverse bore  560  for receiving therein the mounting shaft  524 . To mount the pedals  502   a , 502   b  to the core support  514 , the shaft  524  is rotatably engaged in the mounting brackets  518   a ,  518   b  of the pedals  502   a ,  502   b  and the transverse hole  560  of the upright mounting support  544 . When properly positioned, the mounting shaft  524  extends beyond each side of the horizontal base  526 , and is sized to engage top funnel slot  446  of the channel  402  of the interface  300 , as it will become apparent below. 
     The foot propulsion mechanism  500  also comprises the flexible flappers  542   a ,  542   b  each adapted to oscillate through an arcuate path in a generally transverse direction with respect to the longitudinal axis L 1 -L 1 , about a rotation axis R 2 -R 2  which is at or below the bottom of the hull  24  of the kayak  10  when the propulsion mechanism  500  is mounted to the interface  300 . More specifically, the flexible flappers  542   a ,  542   b  are carried by a shaft  562  extending generally longitudinally and rotatably mounted to the core support  514  via the three flapper mounting brackets  546   a - 546   c . The flappers  542   a ,  542   b  are operatively coupled to the mounting brackets  518   a ,  518   b  of the pedals  502   a ,  502   b  via the cable and chain transmission  540 , which include a pulley  564  mounted to the pulley mounting brackets  558   a ,  558   b , chains  566   a ,  566   b  engaging sprockets (not shown) mounted to the shaft  562  and cables  568  connecting the chains  566   a ,  566   b  to the mounting brackets  518   a ,  518   b . While in the illustrated embodiment the propulsion system  500  is a foot propulsion system, it will be understood that it could also be operated by hand. 
     Having described the general components of the kayak  10  and of the interface  300 , their assembly will now be described, with reference to  FIG.  31   . The body  12  of the kayak  10  may be manufactured using any suitable process, including without being limited to, thermoforming processes, blowmolding processes and rotomolding process. In a specific practical implementation, the body  12  of the kayak  10  may be manufactured by molding two sheets of extrudable material using a thermoforming process to shape the two manufactured sheets into a kayak shape of the type described in the present document, one sheet being used for the top side (i.e. the deck  20 ) and the other for the bottom side (i.e. the hull  24 ) of the kayak  10 . Examples of the different types of thermoplastics that can be extruded include: LDPE, HDPE, ABS, polystyrene, polypropylene, acetates, butyrates, nylons, polyphenylene sulfides, acetals, polycarbonates and thermoplastic rubbers and polyesters, among other possibilities. As it will be appreciated, the well  100  of the kayak  10  may be closed when the deck  20  and hull  24  emerged from the mold after welding. As such, the manufacturing of the kayak  10  may require an opening to be defined in the well post-molding. Typically, such an opening will be carried out by a worker using a cutting tool such as a rotary saw. As it will be understood, the shape of the well (i.e. a generally oblong shape) greatly simplify the cutting of the opening as compared to a more complex hole shape, thereby facilitating the manufacturing of the kayak  10 . 
     The interface  300  is then mounted to the body  12  of the kayak  10 , by first positioning the lower portion  302 . To do so, the snapfits  324   a - 324   d  and fastening projections  332   a - 332   d  are engaged in the oblong well  100  of the body  12 , and is forced upwardly until the snapfits  324   a - 324   d  engage the lip  138  of the third portion  106  of the well  100 , thereby partially securing the lower portion  302  of the interface  300  to the body  12 . When the lower portion  302  is engaged in the well  100  in such a position (i.e. when the snapfits  324   a - 324   d  engage the lip  138 ), the fastening projections  332   a - 332   d  abut the abutment wall  142  of the fourth portion  108  of the well  100 , and the threaded bores  366   a - 366   d  of the fastening projections  332   a - 332   d  are aligned with holes  130   a - 130   d . Furthermore, in such a position, the plate  306  is receive in the recess  152  defined by the peripheral wall  148  and the abutment wall  150  of the fifth portion  110  of the well  100 , while the female portions  334   a - 334   d  of the directing assembly  336 , the guiding fins  334   a - 334   d , the fins  354  of the fastening portions  332   a - 332   d , the fins  376  of the female portions  334   a - 334   d  and the elongated hole  312  are vertically aligned with the open portion of the well  100 . 
     The top portion  304  of the interface  300  is then assembled by positioning the top portion  304  in vertical alignment with the well  100  and gradually lowering down until the top plate  400  is completely received in the recess  116  defined by the peripheral wall  112  and the first abutment wall  114  of the first portion  102  of the well  100 . To properly position the bottom end  403  of the channel  402  in alignment with the elongated hole  312  of the lower portion  302 , a male portions  390   a - 390   d  of the guide assembly  336  gradually engages female portions  334   a - 334   d  of the directing assembly  336 , while the bottom end  403  of the channel  402  gradually engages the inclined edges  358 ,  380 ,  394 , and then the vertical edges  356 ,  378 ,  392  of the guiding fins  334   a - 334   d , the fins  354  of the fastening portions  332   a - 332   d , the fins  376  of the female portions  334   a - 334   d . As such, the directing assembly  336  and the guiding fins  334   a - 334   d , the fins  354  of the fastening portions  332   a - 332   d  and the fins  376  of the female portions  334   a - 334   d  define a guiding assembly and assist in properly aligning the top and bottom portions  302 ,  304  of the interface  300  during their assembly with the body  12  of the kayak  10 . 
     When the top portion  304  of the interface  300  is properly positioned relative to the lower portion  302  of the interface  300  and to the body  12  of the kayak  10 , the fastening projections  462   a - 462   d  of the top portion  304  are received in the recesses  146   a - 146   d  of the second abutment wall  128  of the third portion  106 . Threaded fasteners  132   a - 132   d  are then sequentially engaged into holes  418   a - 418   d  found in the recesses  416   a - 416   d  of the top portion, in holes  130   a - 130   d  of the of second abutment wall  128  and in threaded bores  366   a - 366   d  fastening projections  332   a - 332   d , thereby securing the top portion to the body  12  of the kayak  10  and to the lower portion  302  of the interface  300 . As it will be appreciated, in this position, the second abutment wall  128  of the body  12  is sandwiched between the fastening projections  332   a - 332   d  and  462   a - 462   d  of the lower and upper portions  302 ,  304 , respectively. 
     To further secure the interface  300  to the body  12 , threaded fasteners  120   a - 120   d  are engaged in the oblong holes  414   a - 414   d  defined in the recesses  412   a - 412   d  of the top portion  304 , and in the vertically aligned holes  118   a - 118   d  of the body  12 , until the head of the threaded fasteners  120   a - 120   d  are received in the recesses  412   a - 412   d , to complete the assembly of the interface  300  with the body  12  of the kayak  10 . 
     While in the illustrated embodiment the interface  300  is mounted to the body  12  of the kayak  10  using four threaded fasteners  120   a - 120   d  engaging the top portion  304  of the interface and the body  12 , and four threaded fasteners  132   a - 132   b  engaging the top portion  304  and the bottom portion  302  of the interface, it will be understood that the interface  300  could be mounted to the body  12  of the kayak differently, for instance by using a different number of fasteners, by positioning the fasteners in other locations or by using other types of fasteners (e.g. rivets). As such, the person skilled in the art will appreciate that the number of projections extending from the top and bottom portions of the interface  300 , as well as the number and position of the recesses can be adjusted accordingly. 
     Further, as it will be appreciated, the description of the assembly of the interface  300  with the body  12  of the kayak  10  assumes that the kayak  10  is assembled with the deck  20  in an upside position and the hull  24  in a downside position. As it will be appreciated, the assembly of the interface  300  with the body  12  could be carried out by positioning the body  12  of the kayak upside/down or in any other position. As such, the referring to moving the various elements up or down is in no way intended to limit assembly steps of the kayak  10 . 
     It will also be appreciated that since the interface is secured to the body  12  of the kayak  10  using threaded fasteners and snapfits  324   a - 324   d , the interface  300  can be removed from the body  12 . This may prove advantageous for instance where the operation of the foot propulsion mechanism  500  over time has created damages or weaknesses to the interface  300 . Thus, the interface  300  can be replaced with another interface, thus avoiding the need to replace the entire body of the kayak  10  while ensuring continuous structural integrity of the kayak  10  and the optimum use of the foot propulsion mechanism  500 . 
     Once the interface  300  is properly mounted to the body  12 , the user has the possibility to removably mount the foot propulsion mechanism  500  to the interface  300 , for instance when the kayak  10  is floating on a water surface. To do so, the user engages the lower part of the flappers  542   a ,  542   b  into the channel  402  of the top portion  304 , and gradually lowers down the foot propulsion mechanism  500 . When the core support  514  of the foot propulsion mechanism gradually engages the channel  402 , the left and right transverse projections  548   a ,  548   b  engage lower funnel-shape slots  444  while the shaft  524  engages the top funnel slot  446 . As the foot propulsion mechanism  500  is further lowered down, the shaft  524  forces the lock  450  pivotably mounted in the lock receiving recess  448  toward their unlock position, until the shaft  524  reaches its position in the top funnel slot  446 . In such position, the lock  450  are allowed to pivot back to their lock position, where the convex lower end  454  of the lock  450  engage the shaft  524  to prevent unwanted removal of the foot propulsion mechanism  500 . Furthermore, when the foot propulsion mechanism  500  is properly positioned in the interface  300 , the resting surfaces  554 , 556  provided at the front and rear ends  550 ,  552  of the upright mounting support  544  of the core support  514  lie on the abutments  432 ,  434  of the front and rear slots  428 ,  430  defined in the channel  402 , while the shaft  562  and the flappers  542   a ,  542   b  extend below the hull  24 . As it will be appreciated, the left and right transverse projections  548   a ,  548   b , the shaft  524  and the front and rear ends  550 ,  552  of the upright mounting support  544 , as well as the shape of the horizontal base  526  of the core support  514  (which substantially correspond to the shape of the channel  402 ), collaborated with the various portions of the interface  300  to prevent movement of foot propulsion mechanism  500  relative to the interface  300  during the operation. 
     When the user wants to remove the foot propulsion mechanism  500  from the interface  300 , for instance to facilitate transport of the kayak  10 , the user forces the locks  450  toward their unlock position by engaging the grip elements  458  at the concave upper ends  456 , thereby allowing the shaft  524  to travel upwardly in the channel  402 . The user then pulls on the foot propulsion mechanism  500  to disengage the same from the interface  300 . 
     While the kayak  10  has been described in connection with the embodiment illustrated in  FIGS.  1  to  31   , it will be understood that variations are possible without departing from the scope of the invention. For instance, while the interface  300  and foot propulsion mechanism  500  are described in connection with a kayak  10  provided with a single seat  28 , they could also be used in connection with a tandem kayak, or with any other type of watercraft, including small boats, a paddleboards and pedal boats. Likewise, while the foot propulsion mechanism  500  described in the illustrated embodiment is an oscillating flapper propulsion system, it will be understood that the interface  300  could be used in conjunction with other types of propulsion mechanisms, such as hand operated propulsion mechanisms, motorised propulsion mechanisms such as electric motors and gas motors, whether they are of the flapper oscillating type, propeller type or blade type. Furthermore, the interface  300  could be used in conjunction with a plug configured to be received in the channel  402  and concealing the elongated hole  312  of the interface  300  when no propulsion mechanism is used, for instance when the user propels the kayak  10  with paddles. 
     Furthermore, while the kayak  10  has been described in connection with the interface  300  shown in  FIGS.  11  to  26   , it will be understood that other interface configurations are possible without departing from the scope of the invention. For instance, while the channel  412  extends from the top portion  304  and the elongated hole  312  is defined in the bottom portion  302 , the channel (e.g. channel  412 ) could extend upwardly from a bottom portion (e.g. bottom portion  302 ) while the elongated hole (e.g. elongated hole  312 ) and the fins (e.g. guiding fins  338   a - 338   d ,  354   a - 354   d  and  376 ) could be defined or extend from the top portion (e.g. top portion  304 ). 
     It will also be understood that an interface could be configured to comprise only one of the top and bottom portions (e.g. top portion  304  or bottom portion  302 ), from which would extend a channel (e.g. channel  412 ), either downwardly (in the case of a top portion) or upwardly (in the case of a bottom portion). In such cases, the top or bottom portion would be secured to the body  12  of the kayak  10  using fasteners engaging the top or bottom portion, and the body  12  of the kayak. Taking top portion  304  as an example, to secure the interface constituted by the top portion  304  to the body  12 , threaded fasteners  120   a - 120   d  would be engaged in the oblong holes  414   a - 414   d  defined in the recesses  412   a - 412   d  of the top portion  304 , and in the vertically aligned holes  118   a - 118   d  of the body  12 , until the head of the threaded fasteners  120   a - 120   d  are received in the recesses  412   a - 412   d , to complete the assembly of the top portion  304  with the body  12  of the kayak  10 . 
     Alternatively, the interface could be provided with both a bottom portion (e.g. bottom portion  302 ) and a top portion (e.g. top portion  304 ), but mounted to the body  12  of the kayak  10  differently than interface  300 . For instance, the bottom and top portions could have no fastening projections (e.g. fastening projections  332   a - 332   d  and  462   a - 462   d ), in which case the top and bottom portions would be secured to the body  12  of the kayak  10  by using threaded fasteners engaging either the bottom portion and the body  12  of the kayak, or the top portion and the body  12  of the kayak. Alternatively, various arrangements of snapfits could be used. 
     Tuning now to  FIGS.  32  and  33   , the interface  300  will now be described, in accordance with some embodiments. The interface  300  comprises a first (left) interface section  300   a , and a second (right) interface section  300   b . The first and second interface section being essentially mirror images of one another, only first interface section  300   a  will be described. It will however be appreciated that a similar description also applies to second interface section  300   b , with proper adaptation. 
     The first interface section  300   a  comprises a top plate  302 , a bottom plate,  304  and a first channel section  305  extending between the top plate  302  and the bottom plate  304 . In the illustrated embodiment, the top plate  302  and the bottom plate  304  are spaced-apart and extend generally parallel to one another. The distance separating the top plate  302  and the bottom plate  304  generally corresponds to the distance between the deck  20  and the hull  24 , such that the top plate  302  abuts against the deck  20  while the bottom plate  304  abuts against the hull  24  when the first interface section  300   a  is mounted to the body  12  of the kayak  10 . As such, the first channel portion  305  comprises a top end adjacent to the top plate  302  and a bottom end adjacent to the bottom plate  304 , the distance between the top end and the bottom end of the first channel portion  305  being adapted to permit such abutment of the top plate  302  and bottom plate  304  against the deck  20  and hull  24 , respectively, thereby reducing possible slack between the structures, which could eventually contribute to increased wear and tear. 
     To mount the first and second interface sections  300   a ,  300   b  to the body  12  of the kayak  10 , the first interface section  300   a  is first positioned, by sequentially engaging the bottom plate  304  and the first channel portion  305  in the well  100 , until the top plate  302  and the bottom plate  304  are in general alignment with the deck and hull surfaces. At that point, the first interface section  300   a  can be pushed laterally such that a segment of the rigid body  82  of the kayak  10  surrounding the well  100  is sandwiched between the top plate  302  and the bottom plate  304 . The second interface section  300   b  can then be positioned, again by sequentially engaging the bottom plate  304  and the channel section. As it will be appreciated, the first and second interface sections can be moved into the well and/or relative to one another so as to facilitate the passage of the bottom plate of the second interface section in the well, until the top plate  302  and the bottom plate  304  are in general alignment with the deck and hull surface, respectively. At that point, the second interface section  300   b  can be pushed laterally, in a direction opposite to the first interface section  300   a  such that another segment of the rigid body of the watercraft surrounding the well is sandwiched between the top plate  302  and the bottom plate  304  of the second interface section. In other embodiments either or both of the top plate  302  or the bottom plate  304  are removably attached to the respective channel portion, so that they can be removed in order to slide the channel portion into the well. The removed top and/or bottom plate is then reattached once the channel portion is in the well. 
     At that point, the first and second interface sections  300   a ,  300   b  can be secured to the body of the watercraft by way of a securing assembly. In some embodiments, the securing assembly is configured to secure the first and second interface sections  300   a ,  300   b  to the body by attaching the first and second interface section  300   a ,  300   b  to one another, to thereby prevent movement of the interface  300  relative to the body  12  of the kayak  10 . In an alternate embodiment, the securing assembly comprises a plurality of fasteners engaging each of the first and second interface sections  300   a ,  300   b  and the body  12  of the kayak  10 . In a further alternate embodiment, the fastening assembly is configured to secure the first and second interface sections  300   a ,  300   b  to the body  12  by attaching the first and second interface sections  300   a ,  300   b  to one another, and comprises a plurality of fasteners engaging each of the first and second interface sections  300   a ,  300   b  and the body  12  of the kayak  10 . 
     Together, the first and second interface sections  300   a ,  300   b  define a channel portion  305 . With reference to  FIG.  34   , which is presented to illustrate some principles of the of the channel portion  305  rather that all of the structures thereof, the channel  305  also comprises a first V-shaped recess  440 , a second V-shaped recess  442  terminating into a lower funnel-shape slot  444 , as well as a top funnel slot  446  and a lock receiving recess  448 . At the bottom end  403  of the channel  305 , the first V-shaped recess  440  and the remainder of the channel  305  are sized and shaped to generally conform to the periphery of the core support  514  of the foot propulsion mechanism  500 , while the lower funnel-shaped slot  444  is configured to receive left and right transverse projections  548   a ,  548   b  of the core support  514 . 
     The top funnel slot  446  is configured for receiving therein a mounting shaft  524  of the foot propulsion mechanism  500 . Mounted in each of the lock receiving recesses  448  is a lock  450 . In the illustrated embodiment, the lock  450  comprises a generally elongated flat member  452  including a convex lower end  454  and a concave upper end  456 , the concave upper end  1456  being provided with grip elements  1458  for enhancing contact between a finger of a user and the lock  1450  for releasing the foot propulsion mechanism  500  from the channel portion  1305 . Provided in an intermediate location between the upper end  456  and the lower end  454  is a hole (not shown) for receiving a fastener  1460  for pivotably mounting the lock  450  in the lock receiving recess  1448  of the channel portion  305 . When properly assembled, the lock  1450  is pivotable between an unlock position for allowing the passage of the shaft (shown in dotted line in  FIG.  34   ) and a lock position for preventing the passage of the mounting shaft  524  of the foot propulsion mechanism (shown in continuous line in  FIG.  34   ) to thereby prevent unwanted removal of the foot propulsion mechanism  500  from the interface  300 . In some embodiments, the lock  450  is provided with a bias mechanism (not shown), for instance a coil spring or a torsion spring, to bias the lock  1450  toward the lock position. 
       FIG.  34    is also representative of a cross-section of the interface for any of the other embodiments described herein. 
     With reference to  FIGS.  35 ,  36 A, and  36 B , an alternate embodiment of an interface  1300  will now be described. The interface  1300  can be used instead of interface  300  and comprises a channel portion  1305  configured to receive and support the foot propulsion mechanism  500 . An optional top portion  1304  can be used to to cover/and or conceal the well  100  of the body  12 , regardless of any manufacturing variations which may affect the thickness of the body  12  in this location. 
     More specifically, the top portion  1304  comprises a somewhat annular plate  1308  into which defines a hole  1310  sized and shaped for allowing the passage of the propulsion mechanism  500  therethrough. The optional annular plate  1308  is configured for resting on top of the deck  20 , and for concealing the well  100  while allowing the passage of the propulsion mechanism  500 , to be received in the channel portion  1305 . The annular plate  1308  can be secured to the deck  20  of the kayak  10  using fasteners (e.g. threaded fasteners, rivets and the like), adhesive (e.g. glue, double-sided tape), plastic welded to the deck  20  or can simply rest atop the deck  20 , without any particular fastener or securing means. The channel portion  1305  and/or the annular plate  1308  can also be snap- or friction-fit to the body. In some embodiments, the annular plate  1308  is integrally formed with the channel portion  1305 . 
     With reference to  FIG.  34   , which is presented to illustrate some principles of the of the channel portion  1305  rather that all structures thereof, and using the same reference numerals that interface  300  but in the “1000” range, the channel portion  1305  also comprises a first V-shaped recess  1440 , a second V-shaped recess  1442  terminating into a lower funnel-shape slot  1444 , as well as a top funnel slot  1446  and a lock receiving recess  1448 . At the bottom end  1403  of the channel portion  1305 , the first V-shaped recess  1440  and the remainder of the channel portion  1305  are sized and shaped to generally conform to the periphery of the core support  514  of the foot propulsion mechanism  500 , while the lower funnel-shaped slot  1444  is configured to receive left and right transverse projections  548   a ,  548   b  of the core support  514 . 
     The top funnel slot  1446  is configured for receiving therein a mounting shaft  524  of the foot propulsion mechanism  500 . Mounted in each of the lock receiving recesses  1448  is a lock  1450 . In the illustrated embodiment, the lock  1450  comprises a generally elongated flat member  1452  including a convex lower end  1454  and a concave upper end  1456 , the concave upper end  1456  being provided with grip elements  1458  for enhancing contact between a finger of a user and the lock  1450  for releasing the foot propulsion mechanism  500  from the channel portion  1305 . Provided in an intermediate location between the upper end  1456  and the lower end  1454  is a hole (not shown) for receiving a fastener  1460  for pivotably mounting the lock  1450  in the lock receiving recess  1448  of the channel portion  1305 . When properly assembled, the lock  1450  is pivotable between an unlock position for allowing the passage of the shaft (shown in dotted line in  FIG.  34   ) and a lock position for preventing the passage of the mounting shaft  524  of the foot propulsion mechanism (shown in continuous line in  FIG.  34   ) to thereby prevent unwanted removal of the foot propulsion mechanism  500  from the interface  1300 . In some embodiments, the lock  1450  is provided with a bias mechanism (not shown), for instance a coil spring or a torsion spring, to bias the lock  1450  toward the lock position. 
     In this embodiment, the top portion  1304  (which include the annular plate  1308 ) and the channel portion  1305  are separate components. As it will be appreciated, they can be assembled to the body  12  of the kayak  10  either separately (e.g. the channel portion  1305  is mounted to the body  12  of the kayak  10 , and then the top portion  1304  is mounted to the body  12  of the kayak  10 , the channel portion  1305  and the top portion  1304  have little or no physical interactions with one another) or can be assembled together and then mounted to the body  12  of the kayak as an assembly (for instance, where, as shown in  FIG.  15 B  the top portion  1304  comprises a recess  1312  surrounding the hole  1310  and the channel portion  1305  comprises a corresponding lip  1314 , and the channel portion  1305  is engaged in the hole  1310  of the top portion  1304  and slid until the lip  1314  engages the recess  1312 , with or without adhesive, sealing material fasteners and/or press fit engagement a between them). 
     In an alternate embodiment, in addition to the top portion  1304  and the channel portion  1305 , the interface  1300  could be provided with a bottom portion (not shown in  FIGS.  35  to  36 B ), to conceal the well  100  of the watercraft&#39;s body  12  at the keel or hull  24 . The bottom portion can include its own bottom annular plate with a hole therein for receiving the propulsion mechanism therethrough. In some embodiments the bottom annular plate can be integrally formed with the channel. 
     In a further alternate embodiment, instead of being made from two discrete components (e.g. top portion  1304  and channel portion  1305  of interface  1300 ), the interface could include the same features integrally formed. For instance, with reference to  FIGS.  16  and  17   , there could be provided an interface  1350  including a top portion  1354  and a channel portion  1355  integrated to the top portion  1354 . 
     While the interfaces  300  and  1300  have been described in connection with top portions  304 ,  1304  and  1354 , and optionally bottom portions, it will be appreciated that such top and/or bottom portions could be omitted. For instance, and referring to  FIG.  39   , and interface  2300  devoid of top portion and bottom portion could be provided. In this embodiment, the interface  2300  would correspond essentially to the channel portion  1305  of the interface  1300 , with some adaptation. For instance, and still referring to  FIG.  39   , the interface  2300  comprises a generally vertical lower portion  2302  and a generally vertical upper portion  2304  wider than the lower portion  2302 , the lower and upper portions  2302 ,  2304  being joined together by a transverse resting portion  2306 . In this embodiment, the body  12  of the kayak can be configured to include a seat portion  2308  onto which the transverse resting portion  2306  of the interface  2300  rests. 
     Much like the channel portion  1305  of the interface  1300 , the interface  2300  comprises channels and/or retaining mechanism for mounting the prolusion mechanism to the interface  2300 . 
     In other words, depending on the embodiment, the interface can have only the channel, the channel and a top plate, the channel and a bottom plate, or the channel with both the top and bottom plates, all of which can be separate components or integrally formed with one another. 
     While in the above embodiments, the interfaces  300 ,  1300 ,  1350  and  2300  were configured to be mounted to the body of the watercraft, an interface could instead be permanently or semi-permanently mounted to the propulsion mechanism (e.g. propulsion mechanism  500 ), and be configured to be removably mountable to the body of the watercraft (i.e. the propulsion mechanism and the interface are jointly positioned to and/or removed from the body of the watercraft). 
     For instance, and referring to  FIGS.  40  and  41   , the foot propulsion mechanism  500  secured to an alternate embodiment of an interface  3300  is shown. In the illustrated embodiment, the foot propulsion mechanism  500  is an oscillating flapper propulsion system and comprises a set of left and right pedals  502   a  and  502   b  extending upwardly from the top portion  304  of the interface  3300  when the foot propulsion mechanism  500  is properly mounted thereto. The pedals  502   a ,  502   b  are operatively mounted to a pair of oscillating, flexible flappers  542   a ,  542   b  via a cable and chain transmission supported on a core support  514 . 
     More specifically, the pedals  502   a ,  502   b  are adapted to be alternatively pushed by the user&#39;s feet to actuate the foot propulsion mechanism  500 . Each of the left and right pedals  502   a ,  502   b  comprises a shaft  506   a ,  506   b  including a lower end and an upper end  510   a ,  510   b , as well as a footrest  512   a ,  512   b  for receiving one corresponding foot of the user. The lower ends  508   a ,  508   b  of the shafts  506   a ,  506   b  are mounted to the core support  514 , which is configured to extend longitudinally (i.e. along the longitudinal axis L 1 -L 1  of the kayak  10  when the propulsion mechanism  500  is mounted to the interface  300 ), via a pair of mounting brackets  518   a ,  518   b . Each mounting bracket  518   a ,  518   b  allow adjustment of the distance between the footrests  512   a ,  512   b  and the seat  28  by way of an adjustment bolt engaging the lower ends of the shafts  506   a ,  506   b  and a plurality of adjustment holes disposed on the mounting brackets  518   a ,  518   b . The mounting brackets  518   a ,  518   b  are also configured for receiving a mounting shaft extending transverse to the longitudinal axis L 1 -L 1  and engaging the core support  514 . The mounting shaft allow rotation of the left and right pedals  502   a , 502   b  relative to the core support  514 , about a rotation axis R 1 -R 1 . 
     The foot propulsion mechanism  500  also comprises the flexible flappers  542   a ,  542   b  each adapted to oscillate through an arcuate path in a generally transverse direction with respect to the longitudinal axis L 1 -L 1 , about a rotation axis R 2 -R 2  which is at or below the bottom of the hull  24  of the kayak  10  when the propulsion mechanism  500  is mounted to the interface  3300 . More specifically, the flexible flappers  542   a ,  542   b  are carried by a shaft  562  extending generally longitudinally and rotatably mounted to the core support  514  via the three flapper mounting brackets. The flappers  542   a ,  542   b  are operatively coupled to the mounting brackets  518   a ,  518   b  of the pedals  502   a ,  502   b  via the cable and chain transmission, which include a pulley mounted to the pulley mounting brackets, chains engaging sprockets (not shown) mounted to the shaft  562  and cables connecting the chains to the mounting brackets  518   a ,  518   b . While in the illustrated embodiment the propulsion system  500  is a foot propulsion system, it will be understood that it could also be operated by hand. 
     In this embodiment, the interface  3300  is mounted to the core support  514  of the propulsion mechanism, and allow movement of the pedals  502   a ,  502   b  and of the flappers  542   a ,  542   b , as well as the positioning of the propulsion mechanism  500  in the well. To prevent unwanted movement relative to the body of the watercraft, or unwanted removal of the interface  3300  from the body of the watercraft, the interface  3300  can be provided with manually operable fasteners (e.g. knobs, clamps) or snap mechanisms coupled to pull-out tabs. 
     In addition to interfaces  300 ,  1300 ,  1350 ,  2300 , and  3300  that substantially surround or circumscribe an opening of the channel  402  in the body  12  of the kayak  10  when mounted to the kayak  10 ,  FIG.  42    shows embodiments in which an interface  4300  is formed by separate mounting components that engage only portions of the channel  402 . The interface  4300  engages directed with the body  12  of the kayak  10 , as shown in  FIG.  42   . In some embodiments, the interface  4300  engages with a second interface similar to the interface  1350  shown in  FIG.  38    and connects to the body  12  of the kayak  10  via the interface  1350 . 
       FIG.  42    shows the propulsion mechanism  500  secured via the interface  4300  to the channel  402  of the kayak  10 . The interface  4300  includes a first group of mounting brackets  4302  and a second group of mounting brackets  4304 . In some embodiments, the mounting brackets  4302  are larger than the mounting brackets  4304 . The larger mounting brackets  4302  are positioned to extend substantially parallel to a longer dimension (e.g., a major axis) of the oval-shaped opening  4354 . The smaller mounting brackets  4304  are positioned to extend substantially perpendicular to the longer dimension (e.g., a major axis) of the oval-shaped opening. The mounting bracket  4304  on the right side of the  FIG.  42    shows a cross-sectional view of the mounting bracket  4304  on the left side of the  FIG.  42   , and both mounting brackets  4304  have the same size. The mounting bracket  4302  on the left side of the  FIG.  42    shows a cross-sectional view of the mounting bracket  4302  on the right side of the  FIG.  42   , and both mounting brackets  4302  have the same size. 
     In some embodiments, the same mounting brackets may be used (i.e., all four mounting brackets are the same). In some embodiments, different mounting brackets may be used (e.g., four mounting brackets of different sizes and/or designs). In some embodiments, different numbers of mounting brackets may be used (e.g., two, three, five, six, seven, or eight, etc.). In some embodiments, the mounting brackets  4302  and  4304  allow adjustment in the placement of the propulsion mechanism  500  within the opening  4354 . 
     The mounting brackets  4302  have two portions  4306   a  and  4306   b  arranged perpendicularly in an L-shape configuration. The mounting bracket  4304  has two portions  4308   a  and  4308   b  arranged perpendicularly in an L-shape configuration. The portion  4306   a  (and  4308   a ) is mechanically engaged to a top recessed portion  4350  of the opening of the channel. In some embodiments, as shown in  FIG.  42   , the recessed portion  4350  is defined in the deck  20 . Similarly, a corresponding rim  4356  is also defined in the hull  24 . The rim  4356  is connected to the channel  402 , which is formed by a wall that extends from an edge of the recessed portion  4350  to the rim  4356 . A lip extension  4352  of the recessed portion  4350  provides frictional and tensional engagement for the mounting brackets  4302  and  4304  to snap on. For example, tension from the lip extension  4352  pushes on the second portion  4306   b  of the mounting bracket  4302  to retain the mounting bracket  4304  in the opening  4354 . Additional fasteners (e.g., threaded screws, knobs, clamps, snap fasteners etc.) can be provided via openings  4310  (e.g., threaded openings) to further secure the mounting bracket to the opening  4354 . 
     In some embodiments, the second portion  4306   b  of the mounting bracket  4302  is secured to the propulsion mechanism  500  via a fastener  4312 . The portion  4308   b  of the mounting bracket  4304  includes a protrusion  4314  on which a portion of the propulsion mechanism  500  rests. In some embodiments, the protrusion  4314  is a bottom wall connected to side walls  4316  of the portion  4308   b . A portion of the propulsion mechanism  500  slides into a channel formed by the side walls  4316  and rests on the protrusion  4314  that forms the bottom wall of the channel. 
       FIG.  43    shows an interface  4400  that includes two mounting brackets  4402 . Each of the mounting bracket  4402  is fastened by a fastener  4404  to a joined portion  4450 . One end of the joined portion  4450  connects a top sidewall  4452  and a bottom sidewall  4454 . The top sidewall  4452  extends from a top plane of the deck  20  and the bottom sidewall  4454  extends from the hull  24 , and the sidewalls  4452  and  4454  meet to form the joined portion  4450 . 
     The sidewalls  4452  and  4454  jointly form a well  4490  between the deck  20  and the hull  24 . A (top) cover  4464  is positioned over an opening of the well  4490  and secured to a step  4458  of the deck  20  via a fastener  4460 . A (bottom) cover  4466  is also positioned over an opening of the well  4490  and secured to a step of the hull  24  via a fastener. The mounting bracket  4402  includes a lower protrusion  4406  that supports a portion of the propulsion mechanism  500 . For example, the shaft  562  of the propulsion mechanism  500  can rest of on the lower protrusion  4406 . A top portion  4408  of the mounting bracket  4402  rests on the joined portion  4450  and allows the fastener  4404  to connect to the body  12  of the kayak  10 . 
       FIG.  43    shows an interface  4400  that includes two mounting brackets  4402 . Each of the mounting bracket  4402  is fastened by a fastener  4404  to a joined portion  4450 . One end of the joined portion  4450  connects a top sidewall  4452  and a bottom sidewall  4454 . The top sidewall  4452  extends from the deck  20  and the bottom sidewall  4454  extends from the hull  24 , and the sidewalls  4452  and  4454  meet to form the joined portion  4450 . 
     The sidewalls  4452  and  4454  jointly form a well  4490  between the deck  20  and the hull  24 . A (top) cover  4464  is positioned over an opening of the well  4490  and secured to a step  4458  of the deck  20  via a fastener  4460 . A (bottom) cover  4466  is also positioned over an opening of the well  4490  and secured to a step of the hull  24  via a fastener. The mounting bracket  4402  includes a lower protrusion  4406  that supports a portion of the propulsion mechanism  500 . For example, the shaft  562  of the propulsion mechanism  500  can rest of on the lower protrusion  4406 . A top portion  4408  of the mounting bracket  4402  rests on the joined portion  4450  and allows the fastener  4404  to connect to the body  12  of the kayak  10 . 
       FIG.  44    shows an interface  4500  that includes two mounting brackets  4502 . In some embodiments, as shown in  FIG.  45   , instead of two (or more) mounting brackets  4502 , an interface  4600  is formed by a single mounting bracket  4602  that surrounds substantially the entire opening of the well  4490 , similar to embodiments described in U.S. Pat. No. 10,829,189, issued on Nov. 10, 2020, entitled “Interface for Mounting a Propulsion Mechanism to a Watercraft,” which is hereby incorporated by reference in its entirety.  FIG.  15    of U.S. Pat. No. 10,829,189, incorporated herein in its entirety, shows an interface  300  formed of a top portion  304  and a bottom section  302  that surround substantially the entire perimeter of an opening that defines a well in the body of the kayak, similar to an interface  4800  shown in  FIG.  47   . 
     In some embodiments shown in  FIG.  44   , the mounting bracket  4502  includes a portion  4504  along a top plane of the deck  20 , and a wall portion  4506  that includes a protrusion  4508 . The protrusion  4508  supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the protrusion  4508 . Each of the mounting bracket  4602  is fastened by a fastener  4510  to a step  4558  extending form the deck  20 . 
     A bottom mounting bracket  4512  includes a protrusion  4514  having a channel that allows a fastener  4516  to secure the bottom mounting bracket  4512  to the mounting bracket  4502 . Instead of individual mounting brackets  4512  as shown in  FIG.  44   , an integral bottom portion  302  shown in  FIG.  15    of U.S. Pat. No. 10,829,189 may be used. 
       FIG.  45    shows an interface  4600  formed by a single mounting bracket  4602  that surrounds substantially the entire opening of the well  4490 , similar to the top portion  304  shown in  FIG.  15    of U.S. Pat. No. 10,829,189. The interface  4600  does not include a bottom mounting bracket or an integral bottom portion  302 . The mounting bracket  4602  includes a portion  4604  in a surface plane of the deck  20 , and a wall portion  4606  that includes a protrusion  4608 . The protrusion  4608  supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the protrusion  4608 . The mounting bracket  4602  is fastened by a fastener  4610  to a step  4558  extending form the deck  20 . 
     The mounting bracket  4602  includes additional protrusions that fit a profile of the top sidewall  4452  and joined portion  4450 . The additional protrusions provide more frictional contact between the single mounting bracket  4602  and the deck  20 . 
       FIG.  46    shows an interface  4700  formed by a single mounting bracket  4702  that surrounds substantially the entire bottom opening of the well  4490 , similar to the bottom portion  302  shown in  FIG.  15    of U.S. Pat. No. 10,829,189. The interface  4700  does not include a top mounting bracket or an integral top portion  304 . The mounting bracket  4702  includes a portion  4704  along a bottom plane of the hull  24 , and two side walls  4706  that includes a ledge  4708 . The ledge  4708  supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the ledge  4708 . The mounting bracket  4702  is fastened by a fastener  4710  to a portion  4752  extending from the hull  24  to secure the interface  4700  to the body  12  of the kayak  10 . 
       FIG.  47    shows an interface  4800  formed by a top mounting portion  4802  that surrounds substantially the entire top opening of the well  4490 , similar to the top portion  304  shown in  FIG.  15    of U.S. Pat. No. 10,829,189. The top mounting portion  4802  includes a portion  4806  in a top plane of the deck  20 , and a wall portion  4808  that includes a hook-shaped protrusion  4810  that allows the top mounting portion  4802  to be frictionally engaged (e.g., by snap mechanisms or snap fasteners) to the joined portion  4450 . The top mounting portion  4802  includes a second sidewall  4812 , and a second protrusion  4814 . The second protrusion  4814  supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the second protrusion  4814 . The top mounting portion  4802  is fastened by a fastener  4816  to a bottom mounting portion  4804  of the interface  4800 . 
     The bottom mounting portion  4804  includes a portion  4818  and a raised portion  4820  that lines up with the second sidewall  4812  of the top mounting portion  4802 . The raised portion  4820  is configured to receive the fastener  4816 . The interface  4800  is fastened to the body  12  of the kayak  10  through the hook-shaped protrusion  4810 . 
       FIG.  48    shows an interface  4900  for a well that has a different cross-sectional profile compared to the wells shown in  FIGS.  43 - 47   . Instead of a top sidewall  4452 , a sidewall  4952  includes a first notch  4954   a , a first receptacle  4954   b , and a second notch  4954   c . The interface  4900  does not use any external fasteners, relying on snap mechanisms or snap fasteners integrated in the top mounting portion  4902 . The top mounting portion  4902  includes a protrusion  4904  extending along a top surface of the top mounting portion  4902 . The top surface of the top mounting portion  4902  is offset from a plane of the deck  20 . The top surface is closer, along a height dimension, to the shaft  562  of the propulsion mechanism  500  than a plane of the deck  20 . The protrusion  4904  fits snugly into the first receptacle  4954   b  to provide mechanical (e.g., frictional) engagement between the interface  4900  and the body  12  of the kayak  10 . A second edge  4906  of the top mounting portion  4902  rests on a joined portion  4450  of the well  4990 . A ledge  4908  of the top mounting portion  4902  extends below the joined portion  4450  and supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the ledge  4908 . 
     A bottom plate  4910  is positioned over a bottom opening of the well  4990  and secured to a step of the hull  24  via a fastener  4912 . A top cover  4914  is positioned over a top opening of the well  4990  and secured to a step  4458  of the deck  20  via a fastener  4918 . Instead of a flat plate like the bottom plate  4910 , the top cover  4914  includes a protrusion  4916  having a tapering width along a height dimension. Other profiles of the top cover may be adopted. The top cover  4914  can enhance the aesthetics of the interface  4900  by providing a flat/covered portion to the well  4990  that conceals a portion of the propulsion mechanism  500 . 
       FIG.  49    shows an interface  5000  for a well  5090  that has a different profile compared to the well shown in  FIGS.  43 - 48   . Similar to the interface  4900 , the interface  5000  also does not use any external fasteners, replying on snap mechanisms or snap fasteners integrated in a top mounting portion  5002 . Instead of a top sidewall  4452 , an elongated top sidewall  5052  extends along a substantial portion (e.g., more than 50%, more than 60%, more than 70%, more than 80%, more than 90%, less than 99%) of a height h between the deck  20  and the hull  24 . A tapering profile of channel  5090  formed by the sloping sidewalls  5052  may increase the ease for placing the interface  5000  into the channel  5090 . A shortened bottom sidewall  5054  includes an arched portion  5056  that joins together with the elongated top sidewall  5052  to form a joined portion  5058 . 
     The top mounting portion  5002  includes a portion  5004  along a top surface of the deck  20 , and rest on the step  4458  of the deck  20 . The top mounting portion  5002  includes a first sidewall  5006  and a second sidewall  5008 . The second sidewall  5008  includes a ledge  5010  that supports a portion of the propulsion mechanism  500 . For example, the shaft  562  rests on the ledge  5010 . The first sidewall  5006  includes a hook-shaped protrusion  5012  that allows the top mounting portion  5002  to be frictionally engaged (e.g., by snap mechanisms or snap fasteners) to the joined portion  5058 . The hook-shaped protrusion  5012  fits snugly under the joined portion  5058  to provide mechanical (e.g., frictional) engagement between the interface  5000  and the body  12  of the kayak  10 . The arched portion  5056  may enhance a mechanical strength of the channel and better secure the interface  5000  to the body  12  of the kayak  10 . 
     A bottom plate  4910  is positioned over a bottom opening of the well  5090  and secured to a step of the hull  24  via a fastener  4912 . 
     Having described the general components of the kayak  10  and of the interfaces  300 ,  1300 ,  1350 ,  2300  and  3300 , their assembly will now be described. The body  12  of the kayak  10  may be manufactured using any suitable process, including without being limited to, thermoforming processes, blowmolding processes and rotomolding process. In a specific practical implementation, the body  12  of the kayak  10  may be manufactured by molding two sheets of extrudable material using a thermoforming process to shape the two manufactured sheets into a kayak shape of the type described in the present document, one sheet being used for the top side (i.e. the deck  20 ) and the other for the bottom side (i.e. the hull  24 ) of the kayak  10 . Examples of the different types of thermoplastics that can be extruded include: LDPE, HDPE, ABS, polystyrene, polypropylene, acetates, butyrates, nylons, polyphenylene sulfides, acetals, polycarbonates and thermoplastic rubbers and polyesters, among other possibilities. As it will be appreciated, the well  100  of the kayak  10  may be closed when the deck  20  and hull  24  emerged from the mold after welding. As such, the manufacturing of the kayak  10  may require an opening to be defined in the well post-molding. Typically, such an opening will be carried out by a worker using a cutting tool such as a rotary saw. As it will be understood, the shape of the well (i.e. a generally oblong shape) greatly simplify the cutting of the opening as compared to a more complex hole shape, thereby facilitating the manufacturing of the kayak  10 . 
     The interface  300 ,  1300  or  2300  is then mounted to the body  12  of the kayak  10 , Once the interface  300 ,  1300 ,  1350  or  2300  is properly mounted to the body  12 , the user has the possibility to removably mount the foot propulsion mechanism  500  to the interface  300 , for instance when the kayak  10  is floating on a water surface. To do so, the user engages the lower part of the flappers  542   a ,  542   b  into the channel  402  of the top portion  304 , and gradually lowers down the foot propulsion mechanism  500 . When the core support  514  of the foot propulsion mechanism gradually engages the channel  402 , the left and right transverse projections  548   a ,  548   b  engage lower funnel-shape slots  444  while the shaft  524  engages the top funnel slot  446 . As the foot propulsion mechanism  500  is further lowered down, the shaft  524  forces the lock  450  pivotably mounted in the lock receiving recess  448  toward their unlock position, until the shaft  524  reaches its position in the top funnel slot  446 . In such position, the lock  450  are allowed to pivot back to their lock position, where the convex lower end  454  of the lock  450  engage the shaft  524  to prevent unwanted removal of the foot propulsion mechanism  500 . Furthermore, when the foot propulsion mechanism  500  is properly positioned in the interface  300 , the resting surfaces  554 , 556  provided at the front and rear ends  550 ,  552  of the upright mounting support  544  of the core support  514  lie on the abutments  432 ,  434  of the front and rear slots  428 ,  430  defined in the channel  402 , while the shaft  562  and the flappers  542   a ,  542   b  extend below the hull  24 . As it will be appreciated, the left and right transverse projections  548   a ,  548   b , the shaft  524  and the front and rear ends  550 ,  552  of the upright mounting support  544 , as well as the shape of the horizontal base  526  of the core support  514  (which substantially correspond to the shape of the channel  402 ), collaborated with the various portions of the interface  300  to prevent movement of foot propulsion mechanism  500  relative to the interface  300  during the operation. 
     When the user wants to remove the foot propulsion mechanism  500  from the interface  300 , for instance to facilitate transport of the kayak  10 , the user forces the locks  450  toward their unlock position by engaging the grip elements  458  at the concave upper ends  456 , thereby allowing the shaft  524  to travel upwardly in the channel  402 . The user then pulls on the foot propulsion mechanism  500  to disengage the same from the interface  300 ,  1300  or  2300 . 
     With respect to interface  3300 , the process is essentially similar, except that the interface  3300  is removably secured to and removed from the body of the kayak with the propulsion mechanism attached thereto. 
     In an alternate embodiment, the interface  300 ,  1300 ,  2300 , or similar interfaces or components thereof, could be manufactured such that they be integrated to the body of the watercraft at the time of the manufacture. For instance, in some embodiments, there could be provided a method or process for manufacturing a watercraft including a rigid body having a deck portion, a hull portion and an embedded propeller interface extending between the deck portion and the hull portion by thermoforming, the method or process comprising:
         Providing a mold including a deck shell and a hull shell, the deck shell and hull shell being movable relative to one another between an open position and a closed position;   Providing a propeller interface (e.g. interfaces  300 ,  1300 ,  1350  or  2300 ) including deck end and a hull end, the propeller interface being made of a first plastic material (e.g. by plastic injection);   Providing first and second sheets of a second, thermoformable plastic material;   Moving the deck shell and the hull shell in the open position;   Positioning the first sheet of the second, thermoformable plastic material adjacent to one of the deck portion and the hull portion;   Positioning the second sheet of the second thermoformable plastic material adjacent to the other of the deck portion and the hull portion;   Positioning the propeller interface between the first and second sheets of the second, thermoformable material;   Moving the deck shell and the hull shell of the mold in the closed position;   Simultaneously thermoforming the deck portion and the hull portion to obtain the rigid body;   Moving the deck shell and the hull shell of the mold in the open position; and   Removing the rigid body of the watercraft including the interface from the mold.       

     While the kayak  10  has been described in connection with the embodiment illustrated in  FIGS.  1  to  49   , it will be understood that variations are possible without departing from the scope of the invention. For instance, while the interfaces  300 ,  1300 ,  1350 ,  2300 , and  3300  and foot propulsion mechanism  500  are described in connection with a kayak  10  provided with a single seat  28 , they could also be used in connection with a tandem kayak, or with any other type of watercraft, including small boats, a paddleboards and pedal boats. Likewise, while the foot propulsion mechanism  500  described in the illustrated embodiment is an oscillating flapper propulsion system, it will be understood that the interfaces  300 ,  1300 ,  1350 ,  2300 , and  3300  could be used in conjunction with other types of propulsion mechanisms, such as hand operated propulsion mechanisms, motorised propulsion mechanisms such as electric motors and gas motors, whether they are of the flapper oscillating type, propeller type or blade type. Furthermore, the interface  300 ,  1300 ,  2300  or  3300  could be used in conjunction with plugs configured to be received in the channel and concealing the same when no propulsion mechanism is used, for instance when the user propels the kayak  10  with paddles. 
     The embodiments described above are intended to be exemplary only. The scope of the invention is therefore intended to be limited solely by the appended claims.