Patent ID: 8397658

Claim:
A buoyancy control system comprising: a housing; a first piston supported by the housing such that movement of the first piston changes a volume of a control chamber; a second piston supported by the housing such that movement of the second piston changes the volume of the control chamber; and a source of pressurized working fluid; wherein the first and second pistons are coaxially aligned; the buoyancy control system is operable in a shallow mode in a first range of depths and in a deep mode in a second range of depths; in the shallow mode, fluid flows from the source of pressurized fluid to the first piston such that the pressurized fluid displaces the first piston to alter the volume of the control chamber and thus a buoyancy of the buoyancy control system; and in the deep mode, fluid flows from the source of pressurized fluid to the first and second pistons such that the pressurized fluid displaces both of the first and second pistons to alter the volume of the control chamber and thus the buoyancy of the buoyancy control system.