Oceans clearly play an essential role in life on Earth, yet because of their vastness humans have tended to use their waters as dumping grounds for many waste materials. This practice has increased as land areas for such wastes diminish. Oceans also receive all of the pollutants that are fed to them by the rivers of the world. Even when ships are not actively engaged in dumping wastes, they are themselves sources of pollution most notably, the giant tankers that have caused numerous massive oil spills.

As a result, by the late 20th century ocean studies indicate that what had once been thought impossible is becoming a reality. The oceans as a whole are showing signs of environmental pollution. Even the surface waters of the oceans are increasingly plagued by obvious litter. Some of this litter washes ashore to render beaches unsightly, while other such debris entangles and kills many sea birds and mammals every year.

More insidious than these litter problems are the effects of toxic contaminants from wastes that are dumped in the ocean. These chemicals can upset delicate marine ecosystems as they are absorbed by organisms all along the food chain. Even the paints that are being used on many ships can be hazardous.

The need to address the matter of ocean pollution has been recognized at national and international levels. The U.S. Congress, for example, passed an act in 1988 that would prohibit ocean dumping by 1991, and in that same year 65 nations agreed to cease burning toxic wastes at sea by 1994 should acceptable alternative practices be found. In the late 1990s the latter action remains under debate, however, as several nations continue the practice of ocean burning of toxic wastes. The U.S. act may prove as unenforceable as a prior one in 1977 that attempted the same prohibition. Worldwide, the problem of ocean pollution remains.