Abstract: A water craft (10) includes a hull (12) defining two cavities (18). An inflatable chamber (22) is arranged in each cavity (18), for displacing water from hull (12), in use, to increase the buoyancy of the craft (10). As the chamber (22) is inflated, it expands to reduce the free space available for water in the cavity (18), so as to directly expel water from the cavity (18). The chamber (22) can be deflated, in order to flood the cavity and thereby sink the craft (10). The craft (10) is intended to be operated in a normal buoyant mode and in a submarine mode, and includes propeller means (34). The craft may be in the form of a catamaran-type vessel, a jet-ski, or a submersible tank.

Abstract: A water craft (10) includes a hull (12) defining two cavities (18). An inflatable chamber (22) is arranged in each cavity (18), for displacing water from hull (12), in use, to increase the buoyancy of the craft (10). As the chamber (22) is inflated, it expands to reduce the free space available for water in the cavity (18), so as to directly expel water from the cavity (18). The chamber (22) can be deflated, in order to flood the cavity and thereby sink the craft (10). The craft (10) is intended to be operated in a normal buoyant mode and in a submarine mode, and includes propeller means (34). The craft may be in the form of a catamaran-type vessel, a jet-ski, or a submersible tank.