ocean in Science Expand. The continuous body of salt water that covers 72 percent of the Earth's surface. The average salinity of ocean water is approximately three percent. The deepest known area of the ocean, at 11,034 m (36,192 ft) is the Mariana Trench, located in the western Pacific Ocean. Any of the principal divisions of this body of water, including the Atlantic, Pacific, Indian, and Arctic Oceans.