Ocean Ocean An ocean () is a body of saline water that composes much of a planet's hydrosphere. On Earth, an ocean is one of the major conventional divisions of the World Ocean. These are, in descending order by area, the Pacific, Atlantic, Indian, Southern (Antarctic), and Arctic Oceans. The word "ocean" is often used interchangeably with "sea" in American English. Strictly speaking, a "sea" is a body of saline water (generally a division of the world ocean) partly or fully enclosed by land, though "the sea" refers also to the oceans. Saline water covers approximately and is customarily divided into
Ocean planet Ocean planet An ocean planet, ocean world, water world, aquaplanet or panthalassic planet is a type of terrestrial planet that contains a substantial amount of water either at its surface or subsurface. The term "ocean world" is also used sometimes for astronomical bodies with an ocean composed of a different fluid, such as lava (the case of Io) or ammonia (the case of Titan's inner ocean). Earth is the only known astronomical object to have bodies of "liquid" water on its surface, although several exoplanets have been found with the right conditions to support liquid water. For exoplanets, current technology