Abstract: An apparatus and process for capturing power or mechanical work from the kinetic energy of a moving vessel driven by buoyancy and gravitational forces. The apparatus comprises a main tank, a charging vessel located at the bottom of the main tank, a moving vessel, a compression tank located above the main tank, and a hose connecting the compression tank to the charging vessel. A piston, which is rigidly attached to the moving vessel, moves up and down inside the compression tank compressing the gas therein and forcing it into the charging vessel. When the moving vessel engages a contact valve attached to the charging vessel, the compressed gas enters the moving vessel causing it to become buoyant. The moving vessel is driven by buoyancy and gravitational forces and moves cyclically upward and downward within the main tank, thereby driving an energy recovery means, such as a lever arm, and performing mechanical work.