Seas and oceans are the ultimate sink for much of the waste matter we produce. About three-quarters of the total amount of pollution entering the oceans comes from human activities on land. Seas and oceans can dilute and degrade large amounts of raw sewage, sewage sludge, oil and some types of industrial waste, especially in deep-water areas.

Marine life has also proved to be more resilient than some scientists had expected, leading some of them to suggest that it is generally safer to dump sewage sludge and most other hazardous waste into the deep ocean than to bury them on land or burn them in incinerators.

Other scientists dispute this idea, pointing out that we know less about the deep ocean than we do about outer space.

The marine explorer Jacques Cousteau warned that: "the very survival of the human species depends upon the maintenance of an ocean clean and alive, spreading all around the world. The ocean is our planet's life belt."

Petroleum products 

Heavy metals 

Synthetic organic compounds