Abstract: A passive ballast device, system and method of using same, configured for use with a submersible vehicle in a liquid environment, including a chamber having at least one rigid wall to define at least a portion of a chamber volume, and a passively movable compensator having at least first and second surfaces, the first surface configured to be exposed to the liquid environment, the second surface excluded from the liquid environment, and forming, together with the at least one wall of the chamber, a fluid-tight seal to establish the remainder of the chamber volume, to exclude the liquid environment from the chamber volume and configured to adjust the chamber volume to at least a first chamber volume and a second chamber volume.