An electrochemical engine for buoyancy is provided with the engine having a water-tight and gas-tight chamber containing a volume of seawater. The electrochemical buoyancy engine contributes electrons for reduction of hydrogen protons in the seawater using a sufficient voltage applied to an anode and a cathode disposed in the seawater. The generated hydrogen gas is held in the chamber to provide the desired buoyancy and can be vented to adjust the buoyancy.