Patent Description:
The present invention relates to providing a battery powered propeller driven foot-mounted board for a swimmer or diver.

Known in the art are underwater snorkel or diver hand-operated propulsion devices. For example, the Sea Doo® RS series devices are battery powered using LI-ION lightweight batteries. The handlebar controls are used to hold the device in front of the diver. The unit has a neutral buoyancy. Squeezing two triggers with one's hands powers the unit, and releasing the triggers stops the power to the propeller. Apart from requiring hand operation, such devices tend to have minimal thrust. As used herein, pre-existing hand-held thrust units will be referred to as hand-held propulsion units or generically as "sea scooters.

There is a need in the art to devise a system for adapting existing hand-held propulsion units to be capable of being mounted to a user's back, chest, or feet.

Beyond such an adaptor system, there is a need for a stand-alone device unlike any in the prior art hand-held propulsion units that is specifically designed to be foot-mounted, to be activated by the user's feet, and to allow substantial thrust underwater.

<CIT> discloses a conventional propeller driven surfing device.

According to one aspect of the present invention, there is provided an underwater propulsion device as defined in claim <NUM> hereinafter.

Other aspects of this invention will appear from the following description and appended claims, reference being made to the accompanying drawings forming a part of this specification wherein like reference characters designate corresponding parts in the several views.

The following figures show the device according to the invention: <FIG>, <FIG>.

The rest of figures show further examples of the device not according to the invention.

Before explaining the disclosed embodiment of the present invention in detail, it is to be understood that the invention is not limited in its application to the details of the particular arrangement shown, since the invention is capable of other embodiments. Also, the terminology used herein is for the purpose of description and not of limitation.

Referring to <FIG>, the foot board <NUM> has a left board <NUM> and a right board <NUM>. Each board <NUM>, <NUM> has a central concave cutout so as to encircle the sea scooter <NUM> at about a midpoint of the longitudinal axis A of the sea scooter <NUM>. A latch <NUM> locks the left board <NUM> to the right board <NUM> around the sea scooter <NUM>. A left strap <NUM> attaches the left board <NUM> via a loop <NUM> to the hook <NUM>. A right strap <NUM> attaches the night board <NUM>.

Boots L and R are each attached to the board by an attachment structure. Such an attachment structure may comprise bindings similar to those used for a wakeboard, or water slalom skiing, or water skiing, or snowboarding, or those used for SCUBA fins, or quick dismount boots. A literal boot need not be used, as a user's bare foot may be secured by an attachment structure similar to that of a SCUBA fin, with the foot inserted into a recess or loop, and a loop secured around the heel to hold the foot in place. Where boots are used, the bindings may comprise Velcro straps, ski or snowboard-type bindings. Another embodiment is possible utilizing bindings for boots such as are used for mountain bike pedals, where a snap fitting snaps into place, but may be easily dislodged from the pedal by a deliberate motion of the user's foot. Further attachment structure are discussed below. It is advantageous for such attachment structure to allow for quick-disconnect, so that the rider may easily snap his or her foot out of the attachment structure. It is understood that as used herein, the control of the throttle of the device with the user's foot encompasses the concept of the user's foot being within a boot or the like.

Referring next to <FIG>, the foot board <NUM> attaches the same way as embodiment <NUM> but without the straps <NUM>, <NUM>. For all embodiments bungee cords or straps can be added for assisting with securing the foot board to a sea scooter.

Referring next to <FIG>, the handles <NUM> are received by suitable indents on the left board <NUM> and right board <NUM> of foot board <NUM>.

Referring next to <FIG>, a solid foot board <NUM> has a central hole to fit over the motor housing <NUM> above the handle <NUM>. The taper of the motor housing <NUM> helps sleeve the foot board <NUM> to the sea scooter <NUM>. During use, the propulsive force of sea scooter <NUM> will tend to keep it secure in the central hole of foot board <NUM>. The sea scooter <NUM> may be further secured and stabilized to the foot board <NUM> by the same means previously discussed above.

Referring next to <FIG>, a foot board <NUM> is formed with twin openings for receiving two sea scooters 1a and 1b. A left foot board section <NUM> has a concave opening that fits over the sea scooter motor housing 2b, and a right foot board section <NUM> has a concave opening that fits over the sea scooter motor housing 2a. The left board loop <NUM> has a bungee cord or strap <NUM> attached to handle <NUM> of sea scooter 1b, as well as a loop <NUM> attached to opposite handle sea scooter 1b. Likewise, right board loop <NUM> has a bungee cord or strap <NUM> attached to the outer handle of sea scooter 1a, as well as a loop <NUM> attached to inner handle <NUM> of sea scooter 1a. The left foot board section <NUM> may be separated from the right foot board section <NUM> by a detachable connector <NUM>, such as a latch between the two board sections. This allows the device to be disassembled for easier transport.

Referring next to <FIG>, a self-contained battery foot board <NUM> has a left board <NUM> and right board <NUM> integrated with the housing <NUM> of a water propulsion unit <NUM>, which may comprise a motorized electric propeller powered by lightweight Lithium batteries <NUM> and <NUM> sealed watertight within board <NUM>. Water enters into port <NUM> of the water propulsion unit <NUM>, and is discharged via a propeller from lower port <NUM>. <FIG> is an overhead view of the embodiment in <FIG>. As will be discussed herein, in an embodiment of the device, the propulsion unit can be a trolling motor, as set forth herein, which typically consists of a main torpedo shaped body with a propeller.

In <FIG>, a different embodiment is shown in which foot board <NUM> is separable into left and right halves <NUM> and <NUM>, each with its own separate battery-powered propulsion unit 705a and 705b. As used herein, the term "half' does not literally require that the board be split evenly, and it should be understood that separating the board into two portions of unequal width is encompassed herein so long as the board is otherwise able to support a foot on each of the separate portions. As used herein, the term "portion" of a foot board may be used interchangeably with "half' or "halves" of the foot board.

Here again, slim-profile Lithium ion batteries <NUM> and <NUM> are watertight sealed within the board, with sealed electrical leads extending out to the motors of the propulsion units. The user can lock the left to the right board using locking latch <NUM>, but in a preferred embodiment, latch <NUM> allows the left and right halves of board <NUM> to swivel with respect to one another, such that the user can tip one foot forward while rocking the other backwards, allowing for more versatile directional control when the device is in use. Such a latch might comprise an elastic connection - such as an elastic strap or spring - that allows the halves of board <NUM> to swivel, while also biasing them to return to a neutral position.

A secure lateral connection between halves <NUM> and <NUM> can be aided by a male rod projecting outward along the central axis of the board <NUM> from one of the halves, wherein the rod is configured to mate into a hole on the corresponding side of the other half of the board, thereby allowing one half of board <NUM> to twist relative to the other half about an axis passing through the center of the rod.

A throttle controller <NUM> for the propulsion units could be wireless or with a wire <NUM> as shown. A single controller <NUM> could be configured with separate throttle controls for the propulsion units 705a and 705b, or each propulsion unit could be paired with its own separate throttle controller. Usually, both units 705a and 705b would be controlled at the same speed, but allowing separate throttling will give the user more maneuverability. A microprocessor in the throttle controller could be configured to ensure that the thrust from one of the propulsion units always matches the other propulsion unit, or that the speed differential between one propulsion unit and the other never exceeds a certain threshold. Allowing separate throttle control for the two propulsion units also allows one to be placed into reverse thrust while the other provides forward thrust, thereby allowing the user to spin more quickly. And allowing the user to vary the relative thrust force of the two propulsion units wil allow for greater control and maneuverability. <FIG> is a top plan view of the embodiment shown in <FIG>.

Referring next to <FIG>, a foot board <NUM> is shown with individually pivotable feet as discussed with respect to the embodiment in <FIG>. A linkage <NUM> is provided as a connector having a rotary bearing that enables rotation about an axis running through the board halves. Note that although the foot board has been shown in this and the preceding figures as having a flat surface, it is also possible to hydrodynamically shape the foot board surface to be curved to decrease water resistance when the device is in operation. For example, the edges of the foot board can be made to curve downward away from the boot mounts to allow water to more easily flow around them.

Although the propulsion units depicted in <FIG> have been shown as flat propeller units, it has been found that the device works very well with trolling motors used as the propulsion units. A trolling motor is an underwater electric propeller that is typically attached to a long rod and used as a makeshift outboard motor on small one- or two-man watercraft. A good trolling motor can generate 50lbs or greater of thrust force, and there are models that are even substantially more powerful than that, supplying well over 100lbs of force. Trolling motors are thus notably more powerful than prior art hand-held propulsion unit motor. As used herein, the term "trolling motor" is not limited literally to motors marketed as trolling motors, but to any electric propeller motors of similar construction or power. An example of a suitable trolling motor is a Haswing Protruar 24v, <NUM>,49KW (<NUM> hp) motor, which is rated at <NUM> (<NUM> lbs) of thrust; or a Minn Kota Saltwater Riptide, which is rated at <NUM> (<NUM> lbs) of thrust; or a Newport Vessel, which is rated at <NUM> (<NUM> lbs) of thrust.

A commercially available trolling motor such as those just identified may need retrofitting for operation at depths greater than about <NUM> (<NUM> feet). High pressure gaskets are known in the art of, for example, sealed underwater video-camera equipment, that are more suitable for operation at significant depth than the gaskets found on ordinary commercial trolling motors available as of the time of this writing. Many of such gaskets are often made of polyurethane material or similar polymer. Water-tight sealing for deep diving can also be achieved by designing the motor casing to have multiple rows of gaskets at the sealing joints. The negative space within the motor casing chamber may also be filled with oil to prevent water intrusion during deep diving, with inlet and outlet valves for draining and replacing the oil. High-quality mineral oil is non-electrically conductive and will work for this application, though professional grade transformer oil (as is used in commercial electrical transformers) may be preferable.

Referring next to <FIG> the prior art sea scooter <NUM> has a handle <NUM> and <NUM> with a scooter throttle button <NUM> on each <NUM> side. A throttle lever assembly <NUM> may be fastened to handle <NUM> with a second throttle assembly <NUM> fastened to handle <NUM>. This embodiment has a cable <NUM> within a sheath that is connected to hand controller <NUM> that has an activate trigger <NUM>. Trigger <NUM> pulls the head <NUM> of control cable <NUM> so as to tilt the lever <NUM> against the scooter throttle <NUM>.

<FIG> shows a close-up of an example of a throttle lever assembly. When the cable <NUM> is pulled, it causes lever <NUM> to push down on throttle button <NUM>. <FIG>, show the throttle assembly <NUM> on its own from various angles. In <FIG>, the lever <NUM> is shown in dots in the neutral OFF position. The lever <NUM> hinges around hinge shaft 165a which is mounted to back <NUM>. The back <NUM> has bolts <NUM> fastening it to the block <NUM>. Set screw <NUM> secures the hinge shaft <NUM>. As can be seen, cable <NUM> terminates in end <NUM>, and when cable <NUM> is pulled, end <NUM> in turn pulls down on lever <NUM>, which then presses down on the throttle trigger. <FIG> shows an exploded view of an example throttle lever assembly.

Referring next to <FIG>, a scooter board <NUM> has a mounting hole <NUM> to receive a sea scooter. Brackets <NUM> secure hose clamps <NUM> to lock the sea scooter in mounting hole <NUM>. A protective sheath <NUM> may be used. A right foot plate <NUM> has a heel pivot mount <NUM>, so it can be moved out O or in I by the toe T of the right boot R. A reverse hook up is optional where the toe is pivoted and the heel moves in and out, as will be shown in <FIG>. As the toe T moves in I, the cable end <NUM> pulls the control cable <NUM>, and the lever <NUM> on the trigger assembly <NUM> is depressed into the scooter trigger. Thus, this embodiment enables the user to control throttle by rotating their feet on the surface of the foot board, with the sprint returns tending to bias the feet back to a neutral position.

<FIG> is a bottom perspective view of the embodiment shown in <FIG>, and <FIG> is a top plan view of the same embodiment. <FIG> are like <FIG> except with a reverse mounting of the control cables <NUM>. As can be seen, the spring ball <NUM> pushes the flat spring <NUM> inward during acceleration. As can be seen, the spring <NUM> returns the lever <NUM> to neutral when the user stops pushing in I.

Referring next to <FIG>, the boots L and R are mounted to their respective foot plates <NUM> and <NUM> by an attachment structure (as previously described in connection with to <FIG>). A hole <NUM> allows the cable <NUM> to exit from under the respective foot plates. <FIG> shows a top perspective view of the device wherein the swivels 2002b and 2002d are located at the heel. <FIG> shows a view of the underside of the device from <FIG>. <FIG> is an exploded view of the device, and <FIG> shows the device with a sea scooter inserted.

<FIG>, <FIG> and <FIG> demonstrate how a sea scooter rigged with a wired or wireless throttle controller may be mounded to an L-bracket <NUM> attached to a body plate <NUM> or <NUM> with which has shoulder straps <NUM> for a swimmer. Straps <NUM> secure the sea scooter to the L bracket <NUM>. This L-bracket configuration provides a versatile mounting means. <FIG> shows a foot board embodiment <NUM> that uses L-brackets 3003A and 3003B and straps <NUM> to secure a left and right foot board with boots L and R.

Referring next to <FIG>, quick disconnect boots RQ and LQ have a bottom flange <NUM> that fits into the groove <NUM> on respective left and right foot boards <NUM> and <NUM>. When the sliding lever arm <NUM> is in the neutral position NU, the flange <NUM> can be inserted into the groove <NUM>. When the lever arm <NUM> is moved to the lock position LK shown in dots and the movement for which is shown by arrow LK, the rod <NUM> has passed through a hole HL in flange <NUM>, locking the boots onto respective boards <NUM> and <NUM>. <FIG> shows the arms in the locked position. The boots may be released by pulling the arm <NUM> back to the neutral position.

Referring next to <FIG> an electronic foot control board <NUM> is shown - a plan view of the underside (<FIG> shows the device from the top side). A base <NUM> has a forward carry handle <NUM>. A propeller motor <NUM> may be a DC voltage waterproof type powered by a rechargeable Lithium ion battery. Power leads and wiring are water tight and may be sealed in silicone or the like. A left foot pedal <NUM> has a swivel mount <NUM> to the base <NUM> (a corresponding swivel mount in the right foot board is shown but not labeled). The user's boots strap or interlock securely to the swivel pedal via an attachment mechanism (as previously described in connection with to <FIG>), and the swivel pedal is then capable has a hole that receives and locks to a projection from the underside of the toe of the user's boot, allowing the user to twist their feet in the base <NUM> about an axis running through their toes, causing the heel ends of their boots to move side to side at the rear end of the base <NUM>. Note that this configuration could be easily reversed so that the heel end of the boots mounted to a swivel, and the toe end of the boots was allowed to move side to side.

A magnet (or equivalent transmitter) <NUM> is attached to a rear section of the foot pedal <NUM>, and a magnet (or transmitter) sensor <NUM> is connected to the base <NUM>. The sensor <NUM> has an electronic connection to the motor speed controller <NUM>. The motor speed controller may be a pulse width modulated (PWM) type. The sensor <NUM> may be a hall effect type. The position of the magnet and sensor could be reversed by design choice. The motor speed controller <NUM> is a software flow processor that reads the state of the magnetic sensor <NUM> in the main loop. If the sensor <NUM> has been activated, the processor <NUM> checks if the motor is running. If the motor <NUM> is running and the sensor <NUM> is held in an activated state for greater than X seconds, motor <NUM> is turned off. If the motor is running and the sensor is activated for less than X seconds, the speed is increased one increment (unless already at top speed, in which case nothing happens). If the sensor <NUM> is activated twice in a row and motor is running, speed is decreased one increment (unless already at bottom speed in which case nothing happens). If the motor is off, and the switch is held in activated state for greater than X seconds, motor is turned on at lowest speed.

As a more general matter, it may be appreciated that by virtue of the swivel pedal mounts and sensors, the user is able to control the throttle of the propulsion unit by twisting their boot (and thereby the foot pedal) on the surface of the base <NUM> about the axis of the swivel mount, with a sensor detecting the extent of movement of the opposite (moving) end of the boot, and translating the extent of that movement into a desired amount of throttle. A foot movement other than a swivel may be enabled to control throttle by, for example, including a spring-mounted pedal below the user's toes which functions in a manner similar to an ordinary automobile gas pedal. Such an embodiment is shown in <FIG>.

In the alternative to using the degree of movement of the foot to control throttle, the sensor <NUM> may comprise an electrical switch connected to an electrical circuit and a microprocessor. In the switch embodiment, the microprocessor may be programmed such that each tripping of the switch by a foot movement causes the propulsion unit to cycle through different levels of thrust. For example, each new trip of the switch can increase throttle until a last click drops the throttle back to zero. The processor might also be programmed to change thrust based on a particular pattern of tripping of the switch, such as increasing throttle based on two switch trips in rapid succession. Referring to <FIG>, and embodiment of a foot board <NUM> is shown having propulsion unit <NUM> and a foot pedal mounted to swivel <NUM> and connected to spring return <NUM> which tends to bring the foot pedal back to neutral position when the user does not exert any twisting force on the pedal. A switch <NUM> with a button is affixed to a side extension of foot board <NUM> and positioned such that it may be struck by the foot pedal when the user twists their foot and causes the foot pedal to pivot about swivel <NUM>.

Referring next to <FIG>, the propulsion unit <NUM> has a propeller P shown in <FIG> below the base <NUM>. As shown here, this propulsion unit is similar to that of a trolling motor (previously described) which provides more thrust than a conventional sea scooter. This design does not require any electronics to be mounted to the foot pedal <NUM>. Only the magnet <NUM> (shown in <FIG>) needs to be mounted on the swiveling foot pedal <NUM>. A forward slot <NUM> can guide the foot pedal <NUM> with a stopper <NUM> functioning as a guide post and a maximum travel stopper. A watertight power line supply tube <NUM> is shown leading from the battery compartment within the board to the propulsion unit <NUM>.

Referring next to <FIG> a bracket <NUM> secures the motor <NUM> to the base <NUM>. A right foot pedal <NUM> and duplicate controls are optional. A kill switch <NUM> has a tether <NUM> to the leg of the user (not shown) wherein if the user becomes separates from the board, the user's leg will pull the tether and release the kill switch, turning the propulsion unit off. A spring return <NUM> returns the foot pedal <NUM> to a neutral straight ahead position. A platform spacer <NUM> secures one or more batteries <NUM>. Screws <NUM> are shown as needed. A battery cover <NUM> has fasteners <NUM> to quick connect to platform spacer <NUM>. A gasket traverses the top edge of cover <NUM> and acts to seal the battery compartment when pressed against the spacer <NUM>, and the spacer <NUM> in turn has a perimeter gasket that engages with the underside of board base <NUM>.

An advantage of a board design such as that shown in <FIG> is that the board is formed and configured as having a thin profile of, for example <NUM> (<NUM> inches) or less, and the use of flattened batteries allows the thin profile to be maintained. A thin board of this kind is easily carried by the user, and its total weight with the integrated flattened batteries might only be approximately <NUM>-<NUM> (<NUM>-<NUM> pounds) when the balance of the board is constructed largely of lightweight polymer materials. As used herein, the term "integrated" refers not only to placement within the body of the footboard, but also encompasses direct attachment to or on the foot board.

Referring next to <FIG>. optional repair openings <NUM> for the spring return <NUM> are shown. Referring next to <FIG> the subsystem microcontroller <NUM> C is programmed as shown in <FIG> or with many equivalent logic steps as known to one skilled in the art. A foot pedal movement or a switch (not shown) starts <NUM>. The logic in microcontroller 3309C. The sensor <NUM> is read at <NUM>. If the sensor is activated in <NUM> the logic proceeds to determining if the motor is running at <NUM>. If the sensor held ON at <NUM>, then stop the motor if the motor is running at <NUM>. If the motor was OFF, then start the motor at <NUM>. A double hit at <NUM> either maximizes the speed at <NUM>, or if already at maximum speed, it decreases the speed at <NUM>, a single hit at <NUM> can increase the speed one increment at <NUM>. Other variants on this programming and function are possible. The purpose is to enable the user to control throttle by use of a motion of their feet on the foot board.

Another computer-controlled system that is advantageous to employ with the disclosed devices is that of a depth-activated speed-limiter. In this embodiment, a depth gauge could be incorporated with the foot board, and electrically connected with the throttle control. Pre-set parameters could then be used to regulate the user's throttle based on depth, or the user could modify the parameters while the foot board is in use. Another kind of speed-limiter may be employed to pre-set the maximum speed of the foot board based on the level of skill of the user, or the anticipated diving conditions. Thus, the maximum speed of a beginner could be set lower, or the maximum speed could also be set lower for wreck-driving in close quarters.

Referring next to <FIG> an alternate embodiment remote <NUM> could either replace a foot pedal or augment a foot pedal embodiment for a backup or user choice. An antenna (not shown) would be needed on a microcontroller and receiver (that usually reaches with a radio frequency up to <NUM> (<NUM> feet) underwater). A speed up <NUM> or speed down <NUM> and stop <NUM> button, and start button <NUM> is shown. Such a remote <NUM> could be attached like a watch to the user's wrist.

Although the present invention has been described with reference to the disclosed embodiments, numerous modifications and variations can be made and still the result will come within the scope of the invention. No limitation with respect to the specific embodiments disclosed herein is intended or should be inferred. Each apparatus embodiment described herein has numerous equivalents.

Referring now to <FIG>, an embodiment is shown in which the foot board <NUM> is separated into left and right halves 4105A and 4105B that are releasably connected by magnetic surfaces 4107A and 4107B that form a magnetic linkage when connected. Surface features of the boards, such as swiveling foot pedal mounts and throttle control, are not shown for simplicity. Lithium ion batteries may be sealed within the bodies of the left and right boards, with sealed leads connected to the propulsion units 4111A and 4111B, shown here as trolling motors. As shown in <FIG>, the two halves of the foot board may be snapped together by magnetic attraction. However, the strength of the magnets may be set so as to allow the user to unsnap the two board halves by applying a deliberate spreading force, or by sliding the halves parallel past each other. The magnets may also be configured so as to allow the two foot board halves to pivot individually from each other while remaining connected. Of course, two foot board halves may be joined together by rigid latches, or by a male-female rod connector to form a single connected board, but such a single connected board would not enable relative movement of one half to the other.

Referring next to <FIG>, a foot board <NUM> is shown split into halves 4205A and 4205B. Surface features of the boards, such as swiveling foot pedal mounts and throttle control, are not shown for simplicity. Lithium ion batteries may be sealed within the bodies of the left and right boards, with sealed leads connected to the propulsion units 4211A and 4211B, shown here as trolling motors. A linkage <NUM> holds the halves 4205A and 4205B together. This linkage <NUM> may comprise a rigid rod of fixed length, mounted by bearings or swivel mounts in the inner sides of each half 4205A and 4205B to allow the halves to pivot with respect to one another. For example, one half of the board may protrude a male rod that motes with a bearing on the opposing half of the board. Alternatively, linkage <NUM> may comprise a flexible connector such as a heavy polymer material that tends to return to a straight rod shape, but which may be bent or twisted in infinite directions under force by the user's boots, as shown in <FIG>, thus allowing the halves 4205A and 4205B to assume a wide range of different relative positions and orientations with respect to one other. Alternatively, the linkage <NUM> could be made of a limp yet durable material (such as polymer rope) that allow completely unconstrained relative movement of the halves 4205A and 4205B, while preventing the halves from separating more than the pre-determined distance of the linkage. As known in the art generally of straps, such linkage can be made length adjustable.

Referring to <FIG>, an embodiment is shown of foot board <NUM> wherein a string of watertight LED lights 4311C encircles the perimeter of the board, and may be used to locate divers underwater in dark or murky conditions. Further strings of LEDs 4311A and 4311B are shown encircling the rim on enlarged battery casings 4303A and 4303B designed to accommodate large sized batteries for greater battery life for the combined motor and lighting system.

Referring to <FIG>, an embodiment is shown of board <NUM> that is provided with optional dive weights <NUM> that may be inserted into correspondingly shaped slots in board <NUM>. The board may be constructed so as to be neutrally buoyant in fresh water, with the ability to add weights as ballast in salt water.

Referring to <FIG>, an embodiment is shown of foot board <NUM> that includes a small pressurized air tank <NUM> filled with compressed CO2 or the like capable of being released by the user to inflate bladder <NUM>, which can be used to automatically send the board <NUM> to the surface of the water if the user becomes separated from the board or otherwise wants to send it to the surface separately. A release valve <NUM> is also provided.

Referring to <FIG>, an embodiment 3300A of the foot board <NUM> previously shown in <FIG> is presented wherein the throttle switches are toe pedals <NUM>.

Claim 1:
An underwater propulsion device comprising:
(a) a foot board (<NUM>);
(b) a battery sealed in a watertight compartment (4303A, 4303B) that is integrated with said foot board (<NUM>);
(c) wherein said foot board (<NUM>) comprises two portions (4205A, 4205B), each with an attachment structure for one of said user's feet, and wherein said portions (4205A, 4205B)are connectable to one another by a linkage (<NUM>) that permits said portions (4205A, 4205B) to pivot relative to one another;
(d) wherein said device has two battery-powered underwater propulsion units (4211A, 4211B); and wherein the first of said propulsion units (4211A) is mounted on the first of said portions (4205A) of said foot board (<NUM>) and the second of said propulsion units (4211B) is mounted on the second of said portions (4205B) of said foot board (<NUM>); and wherein each of said portions (4205A, 4205B) of said foot board (<NUM>) has at least one integrated battery in it that is connected by a watertight connection to the one of said propulsion units (4211A, 4211B) that is mounted on that portion (4211A, 4211B) of said foot board (<NUM>);
(e) a throttle control system integrated with said foot board (<NUM>) that allows the throttle of said propulsion unit (4211A, 4211B) to be controlled by a swivel movement of said user's foot, wherein at least one of said foot attachment structures comprises a foot pedal mount that fixes one end of said user's foot to said foot board about a rotational axis that allows the opposite end of said user's foot to swivel from side to side; and wherein said throttle control system further includes a spring return (<NUM>) which tends to bring said user's foot to neutral position when said user does not exert any swivel force with their foot.