US Patent 7328669 Buoyancy-based, underwater propulsion system and method

An apparatus for underwater propulsion. The apparatus may include a hydrofoil, a buoyancy compensator connected to the hydrofoil, a tank containing air, and a controller regulating the passage of air from the tank into the buoyancy compensator. The controller may also regulate the escape of air from the buoyancy compensator. By positioning the hydrofoil underwater and alternating between positive and negative angles of attack, a diver may generate forward propulsion by manipulating the controller to correspondingly alternate the buoyant force produced by the buoyancy compensator between levels below and above neutral buoyancy.