Abstract: The following disclosure discloses a buoyancy compensator having an inflatable bladder at the front and rear of a diver, so that adequate buoyancy is provided with respect to the diver's entire torso. The buoyancy compensator has a strap and harness arrangement that incorporates securement of a backpack thereto for an underwater breathing gas tank that is strapped thereon. The buoyancy compensator includes a low pressure inflation system, an oral inflation member, and a valve for releasing excess pressure either through overexpansion or by manual articulation of the valve cover. A low pressure inflation system for the buoyancy compensator utilizes exhaust breathing gas for pressurization of the buoyancy compensator from the second stage regulator exhaust. The exhaust flow into the buoyancy compensator can be controlled as to pressure and displacement by a pressure relief valve and switching and valving manifold control system.