International Salvage Union (ISU) member salvors provide essential services for the world's maritime and insurance communities. Members are engaged in marine casualty response, pollution defence, wreck removal, cargo recovery, towage and related activities. The principles of salvage and salvage law have evolved over many centuries. A fundamental concept is that the salvor should be encouraged by the prospect of an appropriate salvage award to intervene in any casualty situation to salve the ship, property and, in particular, to save life and prevent pollution. The salvor's right to a reward is based on natural equity, which allows the salvor to participate in the benefit conferred to shipowner, the ship itself and the ship's cargo.