A submarine in-situ net cleaner comprising a skid chassis (1) adapted for smooth and snare free sliding across the surface of said net (2), a buoyancy means (3) associated with said chassis to provide said cleaner with buoyancy, a driving means (4) adapted to cooperate with said net (2) and manoeuvre said cleaner about the surface of said net, a propulsion means (5) adapted to propel said cleaner onto and maintain contact with said net (2) and a cleaning means (6) adapted to remove contaminants from said net including marine fouling from the surface of said net so as to clean said net.