The world ocean, with a volume of 137 × 106 km3, is the largest ecosystem on Earth, and has been used for a variety of purposes by Man for millenia. Many of mankind's uses of the sea are innocuous. Sea routes are still very important for transportation and an important source of food. However, since the industrial revolution it has increasingly become a repository of waste. Owing to its volume and physical properties, the dilution effects are enormous, and, as a result of its chemistry and biology, there is a built-in capacity to recycle much of the deposited waste.

Because of its vast volume and area, the influence of the world ocean on world climate is profound. The phytoplankton of the surface layers regenerate atmospheric oxygen and act as a buffer for CO2, thus moderating any ‘greenhouse’ effect. It is the maintenance of this global balance that emphasizes the importance of keeping the integrity of the ocean and not contaminating it to such a level that its ‘natural’ functions are impaired. However, we must be careful, when considering the disposal of waste, to define what is contamination and what constitutes pollution. GESAMP (1982) defined contamination as ‘the introduction of substances into the marine environment which alters the concentration and distribution of substances within the ocean’. Pollution is defined as ‘the introduction by Man, directly or indirectly, of substances or energy into the marine environment, resulting in such deleterious effects as harm to living resources, hazards to human health, hindrance to marine activities including fisheries, impairment of quality for use of seawater and reduction of amenities’.