In addition to pollution as a direct result of navigation and the exploration and exploitation of the sea bed, the second important source of marine pollution is the disposal of waste produced on land. Direct disposal of land-based waste into the sea has to be considered, but often the method adopted is to transport waste by ship or by aircraft and dispose of it at sea. Disposal of waste at sea, often called ‘ocean dumping’, constitutes 10 per cent of the pollutants and toxic agents that enter the world’s oceans.