Buoyancy control systems and methods

A buoyancy control system for a submersible object submerged in an ambient fluid, comprising a piston housing, a piston member, a pump, control fluid, and working fluid. The piston housing is supported by the submersible object. The piston member defines a piston portion and a shaft portion. The piston member is supported within the piston housing such that the piston portion and the piston housing define a control chamber and an ambient chamber and the shaft portion and the piston housing define a working chamber. The pump is operatively connected to the working chamber. The control fluid is arranged within the control chamber. At least a portion of the working fluid is arranged within the working chamber. Operation of the pump displaces working fluid within the working chamber to displace the piston member to alter a volume of the control chamber.