Sewage, pulpmill wastes, fertilizers, soaps, detergents, radioactive wastes, synthetic fibers, plastics, oils, tars, greases, and insecticides are all pollutants man has placed in our Earth's oceans. Hot and cold water from factories and silt from dredging can also be considered pollutants because they are abnormal to the surrounding water conditions. It is believed the early Viking explorers discovered Greenland and Iceland. When Iceland was found to be a valuable stopping point with lots of vegetation for the Viking explorers, they named it Iceland to confuse invaders. Thus Greenland, which was discovered to be mostly covered with ice, was named so that invaders would travel there instead of the Viking traveler's real stopping point.
Every question leads to another question, and man's present knowledge of the oceans is small.
No more than five percent of the world's ocean floors has been charted with any degree of reliability. In fact, scientists know more about our moon's surface than the bottom of Earth's oceans. Man's ability to predict the ocean environment is restricted to human use, predicting wave height, and conditions for sound transmission.