Floating dock

A floating dock is a U-shaped or pontoon-and-wing-wall steel structure that ballasts down to submerge, receives a vessel over its deck, then deballasts to lift the ship clear of the water for repair. The pontoon provides buoyancy and the keel and bilge blocks that take the docking load; the side walls give transverse stability and carry pumps, services, and cranes. Lifting capacity is rated by pontoon deck load and longitudinal strength, since the docked hull bends the dock like a beam. It is a mobile alternative to a graving (dry) dock, needing no excavated basin, and can be relocated or sold. Design and survey follow classification-society rules for floating docks.