Buoyancy devices

Claim 1

A BUOYANCY DEVICE CAPABLE OF ASSEMBLY ABOUT PART OF AN ARTICLE TO BE BUOYED UP COMPRISING TWO COMPLEMENTARY THIN SHELL PORTIONS OF A SUBSTANTIALLY RIGID SYNTHETIC COMPOSITION, SAID SHELL PORTIONS IN ASSEMBLY DEFINING AN ENCLOSED SPACE THEREIN, AT LEAST ONE SHELL PORTION HAVING ON ITS OUTER EDGE A PAIR OF RECESSES, SAID RECESSES WHEN THE TWO SHELL PORTIONS ARE IN ASSEMBLY DEFINING A PAIR OF APERTURES THROUGH SAID SHELL, EACH SHELL PORTION BEING PROVIDED ON ITS SURFACE WITH AT LEAST TWO HOOKS HAVING CONCAVE SURFACES DIRECTED AWAY FROM THE EDGE OF THE SHELL PORTION, EACH HOOK BEING THE END OF A RIDGE FORMED ON THE SURFACE OF THE SHELL, CORRESPONDING HOOKS ON THE TWO SHELL PORTIONS BEING CAPABLE OF RECEIVING A CONTINUOUS RUBBER BAND STRETCHED FROM A HOOK IN ONE SHELL PORTION TO A HOOK ON THE OTHER SHELL PORTION TO HOLD THE SHELL PORTIONS IN ASSEMBLY, THE SPACE ENCLOSED BY THE SHELL PORTIONS IN ASSEMBLY BEING PARTLY FILLED WITH BUOYANT MATERIAL, AND THE APERTURES THROUGH THE SHELL AND A PORTION OF THE ENCLOSED SPACE WHICH REMAINS UNFILLED WITH BUOYANT MATERIAL PROVIDING A HOUSING FOR PART OF THE ARTICLE TO BE BUOYED UP.