The major oceanic divisions are defined in part by the continents, various archipelagos, and other criteria:
An ocean is a major body of saline water. Approximately 71% of the Earth's surface (~3.6x108 km2) is covered by ocean. The ocean is a continuous body of water that is customarily divided into several principal oceans and smaller seas.
More than half of this area is over 3,000 metres (9,800 ft) deep. Average oceanic salinity is around 35 parts per thousand (3.5%), and nearly all seawater has a salinity in the range of 30 to 38%. Scientists estimate that 230,000 marine species are currently known, but the total could be up to 10 times that number.
Though generally described as several 'separate' oceans, these waters comprise one global, interconnected body of salt water sometimes referred to as the World Ocean or global ocean.