Ocean smoothly into oceans of supercritical hydrogen. The atmosphere of Venus is 96.5% carbon dioxide, which is a supercritical fluid at its surface. On other bodies: 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
Ocean planet simple biological activity over geological timescales. In August 2018, researchers reported that water worlds could support life. An ocean world's habitation by Earth-like life is limited if the planet is completely covered by liquid water at the surface, even more restricted if a pressurized, solid ice layer is located between the global ocean and the lower rocky mantle. Simulations of a hypothetical ocean world covered by 5 Earth oceans' worth of water indicate the water would not contain enough phosphorus and other nutrients for Earth like oxygen-producing ocean organisms such as plankton to evolve. On Earth, phosphorus is washed into