Abstract: An elongated streamlined hull is provided having front and rear ends and a first pair of rear opposite side horizontally outwardly projecting main foils are supported from the hull and have their centers of plan area disposed aft of amidships of the hull. A second pair of forward foils of considerably smaller plan area are mounted from opposite side forward portions of the hull spaced considerably forward of amidships for controlled angular displacement relative to the hull about generally horizontal axes extending transversely of the hull. First control structure is provided for simultaneously adjustably angularly displacing the forward foils and the hull includes front and rear buoyancy tanks, a compressed gas storage tank disposed centrally intermediate the buoyancy tanks and second control structure operatively associated with the storage and buoyancy tanks to selectively flood and blow the buoyancy tanks with ambient water and compressed gas from the storage tank.