A turbine integrated within a hydrofoil extracts energy from a free-flowing motive fluid. In the preferred embodiment, the turbine is of the crossflow variety with runner blades coaxial to the width of the hydrofoil. The foremost edge of the hydrofoil comprises a slot covered by a continuously adjustable gate for controlling the overall drag imposed by the turbine. The hydrofoil mounts to a sailing vessel by means of a gimbal on a structure affixed to the hull, enabling the turbine to optimally respond to changes in direction of the free-flowing motive fluid and facilitating guidance and stability of the vessel. Both axes of the gimbal have a combination of auxiliary generator and motor with a locking mechanism. Engaging the motor and locking mechanism controls the guidance and stability of the overall vessel, and the pitch of the hydrofoil. Disengaging the locking mechanism and motor permits any change in direction of the motive fluid to affect the gimbal thereby extracting energy via the auxiliary generators. To further control drag and output power over a range of flow velocities, the preferred turbine comprises a DC generator with voltage feedback controlling field excitation, coupled to a voltage and current regulating circuit that performs electrolysis of water to produce hydrogen fuel. The hydrogen fuel tank also functions as the vessel's ballast having adjustable draft depending upon its fullness. Integrated remote control simultaneously optimizes vessel guidance, velocity, drag, stability, ballast depth, and electrolysis processes.