Abstract: An apparatus for cleaning ship hulls underwater. A frame is supported by controlled buoyancy tanks which may be flooded to sink the apparatus beneath a ship, blown to a neutral buoyancy for easy underwater maneuvering, or blown to a positive buoyancy so to adhere against the inverted hull of a ship. The apparatus, when underwater against a hull, rides on two independently powered wheels which are individually driven by hydraulic motors for individual control by the diver. These wheels, extending above the upper surface of the apparatus in its submerged position, engage the hull, driving the apparatus along the hull. At the forward end of the apparatus is a reciprocating chipper blade, an angled or concave, hardened steel blade driven by a vibratory impact apparatus at a high repetition rate through a very short stroke.