Marine pollution from crude oil becomes obvious when tanker accidents occur in the vicinity of the coast. But far more crude oil is dumped into the open ocean where tankers have nothing to fear from the authorities. That will change with ENVISAT. Its radar instrument can detect oil spills of less than a few hundred liters through the clouds on the surface of the ocean around the world, day and night. It is thereby possible to determine when ships on the high seas clean their tanks or if drilling platforms are leaking. ENVISAT can also find crude oil clusters which originate from the ocean floor and which indicate new oil deposits.