Patent Publication Number: US-8541439-B2

Title: Formable aquatic coverings for preventing biofouling

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority under 35 U.S.C. 119(e) to the U.S. Provisional Application No. 61/361,725, entitled “Formable Aquatic Coverings for Preventing Biofouling” filed Jul. 6, 2010, the contents of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the protection of structures from damage as a result of continuous exposure to aquatic environments; more particularly to devices which attach to submerged structures, thereby preventing formation of biofouling; and even more particularly to a system for preventing aquatic biofouling containing a propeller enclosure and a formable and disposable propeller glove having anti-aquatic biofouling properties. 
     BACKGROUND OF THE INVENTION 
     The growth and attachment of various marine organisms on structures in aquatic environments, known as biofouling, is a significant problem for numerous industries, including the boating and shipping industry, the oil and gas industry, and the fishing industry. Most surfaces, such as those associated with boat hulls, underwater cables, oil rig platforms, buoys, and fishing nets, which are exposed to coastal, harbor or ocean waters eventually become colonized by animal species, such as barnacles, mussels, bryozoans, hydroids, tunicates, tubeworms, sea squirts, and various plant species. Biofouling results from the interaction of polymeric adhesives produced by the plant and animal species with the substrates for which they are attached. Despite the appearance of simplicity, the process of biofouling is actually complex and involves numerous interactions with many types of microorganisms and macroorganisms. 
     While biofouling creates ecological problems by distributing native plant and animal species to non-native environments, its economic effects are of greater concern. Large amounts of biofouling on ships result in corrosion of the surfaces and the eventual deterioration of the ship. Large amounts of macroorganisms build-up also causes increases in the roughness of the ship&#39;s surface such that the ship experiences greater frictional resistance, decreased maneuverability, and increased drag, resulting in increased fuel consumption. Recreational boaters suffer from the same problems, as barnacles and other animals attach to propellers submerged in water. Navigational buoys or pier posts containing surfaces with large amounts of biofouling are subjected to increased stress resulting from increased weight. This increased stress often results in decreasing the useful life of the structures and necessitating continuous replacement. 
     Various methods have been used in reducing biofouling build-up. One of the more common methods, particularly in the boating and shipping industry, is scraping. However, scraping is labor intensive and environmental issues have been raised over the concerns that scraping results in the increased spread of invasive species. Therefore, there exists a need for devices that eliminate or reduce the amount of biofouling of surfaces exposed to water. 
     DESCRIPTION OF THE PRIOR ART 
     One strategy for protecting objects in contact with water and preventing aquatic biofouling includes the use of physical coverings. These coverings act as protective devices by shielding or separating the structures from the water. For example, U.S. Pat. No. 3,220,374 discloses a marine protective device. The invention is directed towards a unique means and method of protecting marine equipment from the corrosive action of the water and/or marine growth when the boat is not in use. 
     U.S. Pat. No. 3,587,508 discloses an outdrive protective apparatus for easy attachment to a boat. The apparatus protects the outdrive of an inboard-outboard motor from marine growth when the boat is not in use. A bag is placed around the outdrive unit for easy attachment to the transom of a boat in a manner which provides a watertight seal between the bag and the transom and around the outdrive unit. 
     U.S. Pat. No. 3,870,875 discloses a cover for covering the propeller and rear drive assembly of an outboard-inboard motor boat. The cover has an electric taillight mounted to the rear of the cover and which can be electrically connected to the taillight wire of a boat trailer when the boat is mounted on the boat trailer for towing on a roadway. The light serves as a warning to motorists approaching the boat and boat trailer from the rear. 
     U.S. Pat. No. 4,998,496 discloses a shroud for a marine propulsion system which includes a waterproof shroud body that can be fastened to the transom of a boat to surround the outboard portion of the propulsion system. Locking and sealing mechanisms secure the shroud to the boat transom in water-tight engagement and a submersible pump is operable to remove water from the shroud body so that the propulsion system is effectively in dry dock. 
     U.S. Pat. No. 5,072,683 discloses a drainable protective boat motor bag apparatus including a boot defining a bag for fitting over the propeller and stem of an outdrive of a motor mounted on the stern of a boat. The bag includes a channel extending from the mouth to the closed end of the bag for receipt of an open ended hose such that, once the bag has been positioned over the stem, a hose may be inserted for pumping of residual from such bag. A tie string may be incorporated around the mouth of the bag for tying it to the stem and, if desirable, a separate protective sack may be included for covering the propeller blades to protect them from direct exposure to the bag itself. 
     U.S. Pat. No. 5,315,949 discloses an apparatus for protectively covering a motor prop of a boat. The cover includes an adjustable collar, a flexible, opaque bag, and an adjustable collar draw line. The bag has an open top end attached to the collar. A closed bottom end of the bag is opposed to the top end, and has a weight attached thereto. The adjustable collar draw line of the collar is such that with the bag placed over the outcropping, the open end of the bag may be closed around the outcropping by pulling the adjustable collar draw line. The collar includes a locking slot for locking the adjustable collar draw line in place around the outcropping. A manipulation handle removably attaches to the collar for facilitating the placement and removal of the cover onto and off of the outcropping. With the cover in place over the outcropping, water and light are prevented from entering the interior of the bag, whereby water borne life forms such as filter feeding creatures and plant life cannot thrive within the cover. As such, the motor prop is kept virtually free of water borne life forms while the motor prop is covered. 
     U.S. Pat. No. 6,152,064 discloses a protective propeller cover. The cover includes a flexible sleeve into which buoyant material is placed to provide a buoyant enclosure. A flexible propeller cover portion is secured to the flexible sleeve, and the end of the cover is releasably secured about the propeller. The buoyant enclosure is positioned adjacent to the propeller and extends above the water line when the propeller is positioned beneath the water line. The buoyant enclosure serves to protect swimmers from direct contact with the propeller when swimming in proximity to the boat. The protective propeller cover apparatus further serves to protect the propeller during transport or storage. The protective propeller cover apparatus further serves as an anchor cover when the boat is underway. The protective propeller cover apparatus further serves as an emergency flotation device. 
     U.S. Pat. No. 6,609,938 discloses a propeller protector slipper which is used on inboard and outboard motors of boats that are anchored, drifting, aground, docked, in storage, or out of water in transit. The propeller protector slipper ensures protection for the propeller from elements that cause pitting and damage to the propeller, as well as minimizing propeller related injuries. The protector propeller slipper also provides a gage for projecting the distance of the propeller of a trailered boat from a following vehicle. 
     U.S. Publication No. 2008/0020657 discloses an apparatus for protecting the out-drive of a watercraft. The apparatus comprises a locating member adapted for attachment to the underside of the marlin board of the watercraft and a shroud engageable with the locating member to provide an enclosure about the outdrive. The shroud is buoyant and can be floated into sliding engagement with the locating member. The shroud has an opening which is closed upon engagement of the shroud with the transom of the watercraft to preventingress of water into the interior of the shroud. A connection means and the locking means are provided for releasably connecting the shroud to the locating member. 
     In addition to the use of physical coverings as illustrated above, other strategies have been employed in efforts to reduce biofouling. U.S. Publication No. 2009/0185867 discloses a system and method for reducing vortex-induced vibration and drag about a marine element. The system includes, but is not limited to, a shell rotatably mounted about the marine element, the shell having opposing edges defining a longitudinal gap configured to allow the shell to snap around at least a portion of the marine element. A fin can be positioned along each opposing edge of the longitudinal gap, wherein each fin can extend outwardly from the shell. The fins can be positioned on the shell so as to reduce vortex-induced vibration and minimize drag on the marine element. One or more antifouling agents can be disposed on, in, or about at least a portion of the shell, the fins, or a combination thereof. 
     U.S. Pat. No. 7,390,560 discloses a coating system for defouling a substrate. The system includes a ship hull, immersed in water or seawater for long periods of time. The system comprises a conductive layer, an antifouling layer and a means for providing an energy pulse to the conductive layer. The conductive layer comprises polymers, such as carbon filled polyethylene, which are electrically conductive. The antifouling layer comprises polymers, such as polydimethylsiloxane, which have a low surface free energy. The layers are designed such that when the conductive layer is exposed to a pulse of electrical, acoustic or microwave energy or combinations thereof; said conductive layer separates from said antifouling layer. 
     SUMMARY OF THE INVENTION 
     The instant invention describes an anti-biofouling structure for placement onto structures or surfaces that are exposed to aquatic environments. Embedded within the anti-biofouling structure are agents that can diffuse out of the structure and prevent the formation and/or accumulation of plant and animal species. In a particular embodiment, the anti-biofouling structure covers the blades of a boat propeller. Embedded within this structure is the anti-biofouling agent sirolimus. The instant invention also describes a system for preventing biofouling of an object stored in an aquatic environment. The system includes the anti-biofouling structure and a protective cover element constructed and arranged to fit various objects, such as a boat propeller. 
     In one embodiment, the instant invention describes an anti-biofouling structure for placement onto an object exposed to aquatic environments comprising a formable covering material for securing to an object which is in contact with an aquatic environment. The formable covering material comprises at least one anti-biofouling agent, whereby securing of the object with said material results in preventing the formation of biofouling along the surface of the object. The instant invention also describes a system for preventing biofouling of objects which are exposed to aquatic environments comprising a cover having a material containing one or more anti-biofouling agents. The cover has a front surface, an expandable body portion which is traversable between a first position and a second expanded position, an interior portion sized and shaped to enclose an object which is exposed to aquatic environments, and one or more securing members for securing said cover to said object. The system also includes a formable covering material for securing to an object which is in contact with an aquatic environment. The formable covering material comprises at least one anti-biofouling agent, whereby securing of the object with said material results in preventing the formation of biofouling along the surface of the object. 
     In an alternative embodiment, the system includes a first rigid member made of a material containing one or more anti-biofouling materials hingedly securable to a second rigid member. The second rigid member is made of a material containing one or more anti-biofouling agents. Each of the rigid members contains an interior which is sized and shaped to receive an object which is exposed to an aquatic environment. The cover further includes one or more securing members for securing the cover to the object. The system also includes a formable covering material for securing to an object which is in contact with an aquatic environment. The formable covering material comprises at least one anti-biofouling agent, whereby securing of the object with said material results in preventing the formation of biofouling along the surface of the object. 
     In another alternative embodiment, the system for preventing biofouling of objects which are exposed to aquatic environments comprises a flexible cover containing one or more anti-biofouling materials. The cover contains a first face partially connected to a second face and an interior portion sized and shaped to receive a boat propeller. The second face contains a slitted portion terminating in an opening which is sized and shaped to receive a shaft of the propeller. The first face and the second face contain a first member of a hook and loop fastener securing system. The system further includes a strap containing a second member of a hook and loop fastener securing system. The strap is sized and shaped to secure to the first member of a hook and loop fastener securing system. 
     Accordingly, it is a primary objective of the instant invention to provide an anti-biofouling structure which prevents the formation of biofouling on an object which is exposed to an aquatic environment. 
     It is a further objective of the instant invention to provide an anti-biofouling structure which contains anti-fouling agent dispensing strips. 
     It is yet another objective of the instant invention to provide an anti-biofouling structure which contains anti-fouling agents within reservoirs and/or are microencapsulated. 
     It is a still further objective of the invention to provide an anti-biofouling structure in which the anti-fouling agent is sirolimus. 
     It is a further objective of the instant invention to provide a system for preventing biofouling of an object stored in an aquatic environment which includes an anti-biofouling structure and a protective enclosure element. 
     Other objects and advantages of this invention will become apparent from the following description taken in conjunction with any accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. Any drawings contained herein constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  is a simplified illustration of a typical boat propeller system; 
         FIG. 2  illustrates a particular embodiment of the anti-biofouling structure of the instant invention; 
         FIG. 3  illustrates placement of the anti-biofouling structure to the propellers and propeller shaft; 
         FIG. 4  illustrates the anti-biofouling structure in the form of a rolled up sheet; 
         FIG. 5  illustrates a general schematic of an oil rig used to excavate oil reserves in deep waters with the anti-biofouling structure attached to a portion of the rig; 
         FIG. 6  illustrates the use of the anti-biofouling structure with a buoy; 
         FIG. 7A  illustrates a particular embodiment of the anti-biofouling structure in which the diagonally arranged horizontal and vertical elements contain anti-fouling agent dispensing strips; 
         FIG. 7B  illustrates a particular embodiment of the anti-biofouling structure in which the diagonally arranged horizontal and vertical elements contain anti-fouling agents within reservoirs and/or are microencapsulated; 
         FIG. 8A  illustrates a particular embodiment of the anti-biofouling structure in which the horizontal and vertical elements contain anti-fouling agent dispensing strips; 
         FIG. 8B  illustrates a particular embodiment of the anti-biofouling structure in which the horizontal and vertical elements contain anti-fouling agents within reservoirs and/or are microencapsulated; 
         FIG. 9  illustrates a particular embodiment of the protective enclosure element in the form of an expandable bag propeller cover; 
         FIG. 10  illustrates the protective enclosure element in an expanded position; 
         FIG. 11  illustrates an alternative embodiment of the protective enclosure element; 
         FIG. 12  is a perspective view of the back end of the extended protective enclosure element; 
         FIG. 13  illustrates the protective enclosure element with a stiffening plate; 
         FIG. 14  is a frontal view of the protective enclosure element positioned over a boat propeller; 
         FIG. 15  illustrates the protective enclosure element positioned over a boat propeller and secured to the boat propeller shaft; 
         FIG. 16  illustrates both the protective enclosure element positioned over a boat propeller and secured to the boat propeller shaft and the anti-biofouling structure positioned on the blades of the boat propeller; 
         FIG. 17  illustrates a front view of an alternative embodiment of the anti-biofouling structure in the form of a claim shell configuration; 
         FIG. 18  is a rear view of the alternative embodiment of the biofouling structure illustrated in  FIG. 17 ; 
         FIG. 19  is a perspective view of the embodiment of the biofouling structure illustrated in  FIG. 17 , illustrating the components of the clamshell; 
         FIG. 20  is a side perspective view of the alternative embodiment of the anti-biofouling structure; 
         FIG. 21  is a rear perspective view of the alternative embodiment of the anti-biofouling structure shown in  FIG. 20 ; 
         FIG. 22  is a rear perspective view of the alternative embodiment of the anti-biofouling structure shown in  FIG. 20 , illustrating the structure in a closed, sealed configuration; 
         FIG. 23  is a side view of an alternative embodiment of the anti-biofouling structure in the form of collapsible bag-like configuration; 
         FIG. 24  is a side view of the embodiment of the anti-biofouling structure shown in  FIG. 23 , illustrating the bag in a closed, sealed configuration; 
         FIG. 25  is a side view of the anti-biofouling structure shown in  FIG. 24 , illustrating the bag being removed from covering of a propeller. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     While the present invention is susceptible of embodiment in various forms, there is shown in the drawings and will hereinafter be described a presently preferred, albeit not limiting, embodiment with the understanding that the present disclosure is to be considered an exemplification of the present invention and is not intended to limit the invention to the specific embodiments illustrated. 
     The instant invention describes an anti-biofouling structure for placement onto structures or surfaces that are exposed to aquatic environments. While the anti-biofouling structure will be described in the specification as being useful on a boat propeller, one of skill in the art would recognize that the anti-biofouling structure is not limited to boat propellers and may be applied to numerous other structures placed in aquatic environments, such as but not limited to pier posts, buoys, oil rig structures, boat docks, and the like. Accordingly,  FIG. 1  is a simplified illustration of a typical boat propeller  10  having a motor drive system  12 . Attached to the hub  14  are multiple propeller blades  16 . A shaft  18 , which interconnects the hub  14  to the outboard motor drive system  12 , provides a mechanism for rotational movement of the propeller blades  16 . 
       FIG. 2  illustrates a particular embodiment of the anti-biofouling structure  20  in the form of a boat propeller sock. The boat propeller sock  20  has a first end  22  and a second end  24 . The boat propeller sock  20  is placed on the propeller  16  by inserting the distal end  16   a  of propeller  16  into the first end  22  of the boat propeller sock  20  through opening  26 . As the boat propeller sock  20  is positioned over the propeller  16 , the boat propeller sock  20  is aligned such that the first end  22  rests at or near the proximal portion  16   b  of the propeller  16  and the second end  24  of the boat propeller sock  20  rests at or near the distal portion  16   a  of the propeller  16 . In order to fit securely, the boat propeller sock  20  can be constructed to include the same general contoured shape as the propeller.  FIG. 3  illustrates placement of the boat propeller sock  20  on the multiple propeller blades  16 . 
     While the instant invention has been described in the form of a boat propeller sock, the anti-biofouling structure  20  can be shaped to fit any structure.  FIG. 4  illustrates the anti-biofouling structure  20  in the form of a rolled up sheet. As such, the anti-biofouling structure  20  can be placed onto various types of aquatic structures, such as netting, in-take pipes, and sewage pipes.  FIG. 5  illustrates a general schematic of an oil rig used to excavate oil reserves in deep waters. The oil rig  28  sits above ocean water  30 . Support columns  32  and  34  terminate at bases  36  and  38 , respectively, resting at the ground level  40  below the ocean surface. To extend the life of the support and base structures, the anti-biofouling structure  20  can be either embedded within or, as illustrated, simply wrapped around the support column and base.  FIG. 6  illustrates the use of the anti-biofouling structure  20  with a buoy  42 . The anti-biofouling structure  20  can be attached to the portion of the buoy that is near or in direct contact with the aquatic environment to prevent the accumulation of biofouling within those areas. Additionally, anti-biofouling structure  20  can be attached to any of the cables  46  which anchor the buoy  42  to the sea floor. 
       FIGS. 7A ,  7 B,  8 A, and  8 B, illustrate particular embodiments of the anti-biofouling structure  20  which comprise a lattice-like or fenestrate arrangement. Alternatively, biofouling structure  20  may be in the form of a mesh. The anti-biofouling structure  20  contains a plurality of horizontally positioned elements  50  interweaved with a plurality of vertically positioned elements  52 . Both the horizontally positioned elements and the vertically positioned elements may be arranged diagonally, thus forming a crisscross pattern, see  FIGS. 7A and 7B , or alternatively in a parallel fashion relative to each other, thereby forming right angles, see  FIGS. 8A and 8B . While the figures illustrate a significant spacing between the individual horizontal and/or vertical elements, the spacing can be decreased in order to form an anti-biofouling structure  20  which has a tightly knit, weaved pattern with little or no spacing in between. In a preferred embodiment, the horizontally positioned elements  50  and the vertically positioned elements  52 , such as fibers, are made of natural or synthetic plastics, but could be made of other materials such as metals, nylons, cotton, or combinations thereof. The anti-biofouling structure  20  may also be constructed of a biodegradable material such that continued exposure to the aquatic environment results in environmentally friendly degradation. Whichever type of materials are used, the anti-biofouling structure  20  may be constructed such that the structure is formable such that it is capable of being expanded three-dimensionally, radially, longitudinally, or combinations thereof. This constriction allows positioning over an object so that the anti-biofouling structure  20  mirrors the contour of the surface of the object for which it is attached thereto. 
     In order to impart anti-biofouling characteristics, attached to or embedded within the horizontally positioned elements  50  and/or the vertically positioned elements  52  are agents which prevent biofouling. In a preferred embodiment, the anti-biofouling agent is sirolimus having the following chemical structure: 
                         
Sirolimus, also known as rapamycin, is a macrocyclic triene antibiotic originally isolated from the soil microorganism  streptomyces hygroscopicus . Since first being used as an anti-fungal antibiotic, use of Sirolimus has expanded to other fields of medicine. Sirolimus is commonly used as a powerful immunosuppressant drug for preventing rejection after organ transplant surgeries. Research also indicates that Sirolimus can act as a cell-cycle inhibitor, blocking the natural progression of the cell cycle. Other anti-biofouling agents, such as biocides, known to one of skill in the art may be used as well, either individually, or in combination. Anti-biofouling agents which prevent both microfouling, such as biofilm formation and bacterial attachment, and macrofouling, such as attachment of large organisms, including barnacles or mussels, are preferable.
 
     Referring to  FIGS. 7A and 8A , attached to the horizontally positioned element  50  and the vertically positioned element  52  are strips  54 . The strips  54  contain various concentrations of sirolimus and are constructed in such a manner as to leach or diffuse out of the strip  54  and into the external environment, thus preventing the various plant and animal species from attaching or establishing a presence on the anti-biofouling structure  20 .  FIGS. 7B and 8B  illustrate an alternative embodiment of the anti-biofouling structure  20 . The anti-biofouling structure  20  has a reservoir  56  which contains free or microencapsulated sirolimus. The microencapsulation provides a mechanism in which the sirolimus is diffused or released into the environment in a time dependant manner. The sirolimus filled microcapsules  58  can be embedded into the horizontally positioned element  50  and the vertically positioned element  52  without the use of the reservoir  56 . While these mechanisms described above may be the preferred methods for embedding sirolimus within the anti-biofouling structure  20 , other methods of inserting the anti-fouling agent, such as the use of spray-on applications, as known to one of skill in the art is contemplated. Additionally, the anti-biofouling structure  20  need not contain the vertical or horizontal elements but may rather be made of a pliable sheet which contains the anti-fouling agent embedded therein. To provide a securing mechanism, the anti-biofouling structure  20  can include fastening elements, such as but not limited to loop  62  and hook  64  type fasteners, such as VELCRO, or snaps, buttons, glue strips, or zippers. 
     The instant invention further contemplates a system for preventing biofouling of an object stored in an aquatic environment. The system includes the anti-biofouling structure as previously described and a protective enclosure element, which may comprise a material containing one or more anti-biofouling agents.  FIG. 9  illustrates a particular embodiment of the protective enclosure element  64  in the form of an expandable bag. Protective enclosure element  64  has a generally circular shaped front surface  66  and an expandable/collapsible body portion  68 . A portion of the expandable/collapsible body contains accordion-like infoldings  70  which allow the protective enclosure element  64  to be traversed between a first resting or collapsed position, see  FIG. 9 , and a second fully extended position, see  FIG. 11 , or multiple positions between the first and second positions. 
     Attached to the protective enclosure element  64  is a first cable  72  and a second cable  74 . The first cable  72  and the second cable  74  which can be made of rope, plastic, or preferably of stainless steel, connect via attaching element  76 , such as a clip or swage, to a single securing cable or lanyard  78 . When in the extended form, the securing end  80  of the protective enclosure element  64  is exposed and secures the protective enclosure element  64  to a structure or object, such as an exposed shaft of a boat propeller, by way of fastening element  82 , see  FIG. 10 . Fastening element  82  can be connected to the protective enclosure element  64  through a securing string  84 .  FIG. 11  illustrates an alternative embodiment of the protective enclosure element  64 . This embodiment contains the same features as described previously; however, the second cable has a coiled portion  86 . 
       FIG. 12  is a perspective view of the fully extended protective enclosure element  64 . As illustrated, the securing end  80  contains the fastening elements  88  and  90 . The fastening elements  88  and  90  are illustrated as a loop and hook type fastener, i.e. VELCRO, however, the fastening elements may also include snaps, clasps, clip, buttons, zippers, or other fastening type devices known to one of skill in the art. Although not necessary, the securing end  80  may be designed to contain portions  92  and  94  which provide a place in which securing end  80  may be attached to the external aquatic structure. 
       FIG. 15  illustrates the protective enclosure element  64  in the fully extended position and placed over the propeller  16 .  FIG. 16  shows the addition of the anti-biofouling structure  20  to the propeller  16 . In use, the protective enclosure element  64  and the anti-biofouling structure  20  can be secured to the necessary structures with the aid of a diver. For example, the diver encapsulates the protective enclosure element  64  over the propeller  16  by extending the protective enclosure element  64  from the first storage position to the second extendable position. The protective enclosure element  64  is secured to the exposed propeller shaft  18  through the securing element  82 , including but not limited to a gasket such as a closed cell foam ring (not illustrated) and a circlip, see  82 ′  FIG. 9 , commonly used on agriculture equipment. The securing elements can be constructed of plastic or stainless steel materials and can be sized to fit specific sized shafts. The protective enclosure element  64  may also be designed to seal against itself through the use of various sealing methods such as snaps, buttons, or hook and loop fastening systems, such as VELCRO. In a particular embodiment, the securing end  80  of the protective enclosure element  64  is sealed with VECLRO type retention strips  88  and  90  which are attached to the outside perimeter of the protective enclosure element  64 . This provides attachment of the protective enclosure element  64  around the propeller shaft. 
     The protective enclosure element  64  may also include a semi-rigid, rectangular plastic stiffening plate  96 , see  FIG. 13 . The stiffening plate  96  is riveted to the inside of the protective enclosure element  64 . The plate assists in defining the protective enclosure element  64  and will also facilitate the removal process by providing support for the device that triggers release of the protective enclosure element  64  from around the propeller. This balances and facilitates the removal of the protective enclosure element  64 , thus reducing the likelihood of the device becoming ensnared in either the propeller blades or rudder appendages. The circlip  82 ′, which maintains the protective enclosure element  64  seal around the propeller shaft  18 , may be designed to have a looped portion. The VELCRO which is used to seal the forward end of the protective enclosure element  64  on both sides of the forward face also contains a looped portion. The looped portion can be used to clip the circlip together. This prevents the VECLRO connection from becoming unattached and secures the circlip. Once secured in place, the protective enclosure element  64  and the anti-biofouling structure  20 , which has been fitted to the propellers  16 , remain in place without the need for continuous monitoring and re-securing steps, thereby protecting the encapsulated structures from the aquatic environment without any additional efforts from the user. 
     One of the advantages of the system as described herein is that the components of the system are designed for easy removal. The two cables  72  and  74  are positioned on the outside surface of the protective enclosure element  64  and are fed over the top of the propeller blades when the protective enclosure element  64  is fully extended. The two cables may be positioned at points which are 180 degrees from each other when facing the back side of the propeller. Each of the cables may simply be attached to the protective enclosure element  64  via stitching, gluing, or through the use of a small diameter, TEFLON-lined synthetic guide tube  98 , see  FIGS. 10 and 14 . The tube can be secured at one or more points on each side of the outside perimeter of the protective enclosure element  64 . The tubes can be designed to contain a 90 degree bend with an opening facing the aft and the other end facing the propeller shaft. The cables  72  and  74  are secured together with the attaching element  76  to form the single securing cable  78 . The securing cable  78  is led aft and up over a portion of the boat, such as the swim platform or transom, and secured to the inside of the boat through a cleat on each side of the boat with slight tension. When the boat is at rest, the likelihood that the cable becomes entangled by an object and results in creating a strong enough tension so as to dislodge the securing devices is minimal. 
     Once the boat operator decides that the protective enclosure element  64  must be removed, the operator pulls upon the securing cable  78  with a backward force. Such a force simultaneously pulls on the circlip and releases the device from the propeller shaft. The backward force also releases the VELCRO connection, thereby releasing the protective enclosure element  64 . The protective enclosure element  64  is now free to be pulled completely off the enclosed object, i.e. propeller  16 . Once free from the propeller, the boat operator can start the engine, thereby creating rotational spin of the propellers. As the propellers rotate, the anti-biofouling sock  20  is expelled from the propellers into the water. The operator can then simply retrieve the expelled anti-biofouling sock  20  from the water. Alternatively, if the anti-biofouling sock  20  is made of a degradable material, the sock can be left safely in the water to naturally disintegrate. 
       FIGS. 17-19  illustrate an alternative embodiment of the anti-biofouling structure, illustrated generally as  100 . In this embodiment, the structure  100  is formed from a first rigid member  102  and a second rigid member  104  interconnected to form a clam-shell configuration. Each of the rigid members  102  and  104  contain an interior  106  and  108  which is sized and shaped to house a propeller. The outer shell is preferably made from a material, such as plastics or a natural material, such as cotton, having a hardness to retain its shape. Coated into the plastic or cotton material is one or more anti-biofouling, biocide materials. Alternatively, or in combination, a biocide paint may be used to coat the outer surfaces  110  and  112 . In one embodiment, the bottom edge  114  of the first rigid member  102  and the bottom edge  116  of the second rigid member  104  are hingedly connected through a living hinge  118  and  120  or any other hinge mechanism which allows each of the halves to move relative to each other, thereby opening and closing about the hinge. Each of the rigid members  102  and  104  may further contain a cut-out section  122  and  124  which are sized and shaped to allow a rotor shaft to pass through when placed side by side. 
     Referring to  FIG. 18 , when the first rigid member  102  is aligned with the second rigid member  104 , the cut out sections  122  and  124  form an opening  126 . When the structure  100  is placed over a rotor, the shaft connecting to the rotor passes through the opening. To secure the first rigid member to the second rigid member, the top surface  128  of the first rigid member  102  and the top surface  130  of the second rigid member  104  contain one locking member of a locking mechanism. As illustrated, the top surface  128  contains an eyelet  132  which is positioned to align with in a parallel fashion, or overlap, a second eyelet  134  attached to the top surface of  130  when the two rigid members are closed together. A securing member, illustrated herein as a cotter pin  136 , may be used to secure the two members together. Preferably, the cotter pin  136  is secured to a portion of a lanyard  138 . A second portion of the lanyard  138  is attached to either half of the clam shell halves. As shown in  FIG. 18 , the lanyard  138  attaches to the bottom surface area  140  of the first half  102  or the bottom surface  142  of the second half  104  through, for example, an eyelet  144 . The amount of lanyard which attaches to the cotter pin  136  is preferably less than the amount of lanyard used to attach to the bottom. In this manner, pulling on the handle attached to the lanyard  138  results in pulling the pin  136  from the overlapping eyelets  132  and  134  first. As the lanyard  138  is continually pulled back, at some point a tension is formed on the part of the lanyard that is connected to either of the rigid members  102  or  104 , resulting in the pulling apart of one or both of the rigid members  102  and  104 . Although not illustrated, each of the halves may contain a weighted section to allow them to sink below the boat. Since they remain attached to the lanyard, the user can simply retrieve the halves by pulling on the lanyard  138 . Alternative securing mechanisms, including buttons, snaps, zippers or other means known to one of skill in the art can be used as well. 
     Referring to  FIGS. 20-22 , an alternative embodiment of the anti-biofouling structure is shown and illustrated as a bag-like cover  146 . The bag-like cover  146  is preferably made of a pliable plastic or natural fiber material which is impregnated, encapsulated, or coated with a biocide material. The bag-like cover  146  contains two panels  148  and  150 , see  FIGS. 20 and 21 . Panel  148  contains a face  152  which forms the front portion of the bag-like cover  146  and an edge  154  which traverses the perimeter of the face  152 . The panel  150  contains a face  156  which forms the back portion of the bag-like cover  146 . An edge  158  traverses the perimeter of the face of  156 . The panels  148  and  150  interconnect through edges  154  and  158  to form an interior portion  160 . The interior portion  160  is sized and shaped to receive a structure, such as a boat propeller, which needs to be protected from the effects of biofouling. Preferably, the two panels  148  and  150  are partially interconnected through a fastening mechanism, such as stitching  162  or chemical means. 
     As illustrated in  FIG. 21 , a portion of the bag-like cover  146  does not provide for the panels  148  and  150  to be interconnected by stitching  162 . This configuration provides for an opening  164 . The opening  164  provides a means for the bag-like cover  146  to be arranged over a structure or object which needs to be protected from biofouling. Once secured over the object, bag-like cover  146  can be closed through securing members such as buttons, snaps, zippers, or other means known to one of skill in the art. In a preferred embodiment, the securing members are preferably a loop and hook type fastening system, i.e. VELCRO. Accordingly, a portion of the edges  154  and  158  or the faces  152  and  156  may contain the VELCRO loops  166  secured through, for example stitching or chemical fastening, their surfaces. An externally attached strap containing VELCRO hooks is used to fasten the edges  154  and  158  together. By placing edges  154  and  158  in close proximity, the strap  168  containing the VELCRO hooks is placed over the VELCRO loops  166  portions, see  FIG. 22 . 
     As illustrated in  FIG. 21 , the back face  156  contains a slitted portion  170  which terminates in a portion of the bag which extends outwardly facing cylindrical shape  172 . The slitted portion  170  provides for the bag-like cover to enclose an object which contains portions which may not need to be covered. For example, the cylindrical shape  172  shown in  FIG. 21  is designed to allow the bag-like cover  146  to enclose the propeller of the boat but allow the propeller shaft  174  to extend out. The portions of the face  156  that defines the slitted areas can be covered with VELCRO loops as described above. Aligning the areas in close proximity allows a second strap  176  containing VELCRO hooks to be placed on top to secure them together around the circumference of the propeller shaft  174 . Each of the straps  168  and  176  may contain one or more attached O-rings (not illustrated). One or more lanyards (not illustrated) may be attached to the O-rings. Pulling the lanyards away from the cover provides a force that results in removal of the straps  168  and  176  from the VELCRO loops  166 . Fastened to the interior portion of the cover  146  may be one or more D-rings (not illustrated) which preferably attach to one or both straps  168  and  176  through, for example, stitching. Once coupled to the D-rings, the straps  168  and/or  176  remain connected to the bag thereby reducing the risk that they will be displaced. One or more openings along the surface of the bag may be utilized to allow the straps to exit the interior portion and couple to the VELCRO loops  166 . Once the straps are removed from the VELCRO loops  166 , the bag is partially opened and it can be removed from covering the object. 
     Referring to  FIGS. 23-25 , an alternative embodiment of the anti-biofouling structure is shown and illustrated as bag  178 . The bag  178  is preferably constructed of a collapsible plastic material, similar to a standard garbage bag, and is impregnated or coated with a biocide material. The bag  178  contains a main body comprising an opening which is sized and shaped to allow a structure to be stored within the interior portion  184 . The outer edges  186  and  184  may be made of a stronger material than that of the body to allow the bag  178  to maintain some shape. Tightening members, illustrated herein as drawstring  190  and  192 , are used to enclose the bag  178  over the object. Drawstring  190  and  192  are preferably constructed in such a manner that, as the first drawstring  190  is pulled toward the second drawstring  192 , opening  182  is reduced. Additionally, the drawstring  190  and  192 , when pulled together maintain a tension so that when they are not secured together, they retract back to their original, non-pulled state. The drawstrings  190  and  192  contain eyelets  194  and  196  which align together when the two drawstrings are pulled toward each other. A securing member, such as a cotter pin  198  is used to secure the drawings together. In a similar manner, as described before, the cotter pin  198  can be secured to a string  200 . The opposite end of the string  200  may be attached to the bag  178  at a canvas strap  202 . Pulling on the canvas strap  202  results in dislodging the cotter pin  198  from the eyelets  194  and  196 . Once the eyelets are no longer secured to each other, the drawstrings  190  and  192  retract, opening the bag and exposing object, illustrated herein, as a boat propeller  204 , see  FIG. 25 . 
     All patents and publications mentioned in this specification are indicative of the levels of those skilled in the art to which the invention pertains. All patents and publications are herein incorporated by reference to the same extent as if each individual publication was specifically and individually indicated to be incorporated by reference. 
     It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and any drawings/figures included herein. 
     One skilled in the art will readily appreciate that the present invention is well adapted to carry out the objectives and obtain the ends and advantages mentioned, as well as those inherent therein. The embodiments, methods, procedures and techniques described herein are presently representative of the preferred embodiments, are intended to be exemplary and are not intended as limitations on the scope. Changes therein and other uses will occur to those skilled in the art which are encompassed within the spirit of the invention and are defined by the scope of the appended claims. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention which are obvious to those skilled in the art are intended to be within the scope of the following claims.