Three-quarters of the Earth's surface is water, including oceans, coral reefs and estuaries. The open ocean zone includes those ocean waters furthest from land. The open ocean represents 65 percent of the Earth's total oceans.
According to the World Wildlife Fund, parts of the open ocean have almost no life, while other parts have large numbers of species. About 10 percent of the world's marine life is found in the open ocean. Because the open ocean is so vast, predators are required to travel long distances quickly to find sources of food. Many species, such as marlin, tuna and dolphins, are fast swimmers.
Research published in 2010 by the University of Sheffield found that the open ocean is the part of the ocean scientists know the least about. The study said that the area between the ocean surface and the ocean floor -- long thought to be absent of larger mammals -- is teeming with life.
