Abstract: A gas or fuel cap has a relatively large diameter upper section and a relatively small diameter lower section. Threads are formed on the lower section which engage with a filler tube or conduit of a fuel storage tank mounted on a watercraft. One or both of the upper and lower sections is formed of an enhanced polyurethane material. The enhanced polyurethane material is formed by injecting a micro balloon filler into a mold containing a polyurethane. The result is a gas cap formed from a material, the enhanced polyurethane, which is buoyant.