After the oil is contained, it must be recovered from the water. A skimmer is a mechanical recovery device designed to remove the oil from the water's surface without causing major alterations in its physical or chemical properties.
All skimmers work best in calm waters with little or no wave action.
Viscosity of the spilled oil determines the most appropriate skimmer and pump types for a particular incident. Lower viscosity substances are lighter and when spilled spread out over a greater area. Higher viscosity oils do not spread out as much and remain thicker. A weir skimmer is an example of a suction skimmer. A rope mop skimmer is an example of an adhesion skimmer.