A mechanism for steering and stabilizing hydrofoil watercraft comprising mounting submerged foils under the stern in a plane parallel to the fore and aft lines of the craft and pivoted on an axis lying in a plane perpendicular to those fore and aft lines. When these submerged foils are then provided with a means for independently turning them from inside the craft, they form an effective method of turning the craft with reduced side slippage, especially if they are extended outboard of the craft.

A unique water ski device for use with a tow rope for allowing the rider to ride on, above or below the surface of the water, includes a riding platform rigidly affixed above a hydrofoil by a detachable bent pole, flanged on each end, so that it can be dismantled for easy transport and storage. The riding platform has a ski handle affixed by ropes for use by the rider as a balancing aid. The riding platform has a nonskid surface for the safety of the user. The length of the pole can be of various lengths up to and above 10 feet in length. The device is towed behind a boat by means of a two rope which is affixed to the forward end of the riding platform. The rider rides on the top of the riding platform in a standing position and by shifting his or her weight forward or backward controls the height of the device above, on or below the water surface.

The invention is gas-filled cavities that reduce drag on the underwater surfaces of marine vehicles. Hydrofoils, struts, boat and ship hulls, pontoons, underwater bodies, fins, rudders, fairings, protuberances, submarine sails and propulsors are underwater surfaces that may be covered by the gas-filled cavities to reduce drag on them. The gas-filled cavities are to be used on underwater surfaces of marine vehicles, such as hydrofoil craft, monohulls, catamarans, SWATH (small waterplane area twin hull) craft, SES (surface-effect ships) and WIG (wing-in-ground effect) vehicles. Each gas-filled cavity is formed by ejecting air near the end of each nosepiece. Air is ejected at a speed and direction which is close to that of the water at the local cavity wall. The cavity is formed behind the nosepiece. The nosepiece is adapted to control the shape of the cavity. Cavity length is also controlled through controlling air ejection rates, and through the use of a tailpiece to close the cavity within a limited region near the front of the tailpiece.

A water sports device for supporting a seated human rider while the rider and the device are towed behind a powered water craft,, including an elongate board to which a seat and foot holder are secured, an elongate arm extending downward from the board and a planing blade secured to the arm generally parallel to the board so that the planing blade provides essentially no lift when the board is horizontal. The positioning of the seat and the planing blades at the rear of the board, the use of a single vertical strut, the size of the planing blade and the positioning of the foot holders at least two feet in front of the seat provides a water sports device which is relatively easy to ride,, while at the same time being highly maneuverable and capable of high jumps.

A water sports device for supporting a seated human rider while the rider and the device are towed behind a powered water craft, including an elongate board to which a seat and foot holder are secured, an elongate arm extending downward from the board and a planing blade secured to the arm generally parallel to the board so that the planing blade provides essentially no lift when the board is horizontal. The positioning of the seat and the planing blades at the rear of the board, the use of a single vertical strut, the size of the planing blade and the positioning of the foot holders at least two feet in front of the seat provides a water sports device which is relatively easy to ride, while at the same time being highly maneuverable and capable of high jumps.