Submersion moving plane skimmers present a moving plane, typically a conveyor-belt like material, to the oil/water interface and directs it under water to a collection well. The collection well has discharge ports along its bottom, allowing water to be released and providing gravity oil/water separation. With some designs, a wiper assembly at the collection well assists in removing viscous oil from the belt. The skimmer may be used in a stationary or advancing mode. In a stationary mode, oil is moved solely by adhesion to the belt; in advancing mode this is supplemented by hydrodynamic forces.