A sea is either a large expanse of saline water connected with an ocean, or a large, usually saline, lake that lacks a natural outlet such as the Caspian Sea and the Dead Sea. Colloquially, the term is used synonymous with ocean. Large lakes, such as the Great Lakes, are sometimes referred to as inland seas. Marginal seas are those that have currents caused by ocean winds, and mediterranean seas are those in which currents are caused by differentials in salinity and temperature.
International Hydrographic Organization
The International Hydrographic Organization (IHO) is the international authority that sets forth nomenclature and definition of bodies of water. The IHO's Limits of Oceans and Seas was first published in 1928, with its current working document the third edition published in 1953. A fourth draft edition was proposed in 1986 but has yet to be ratified due to outstanding issues such as the Sea of Japan naming dispute.
List of seas
† Not listed in IHO S-23 4th ed. (There are 113 Seas on Earth.)
Some bodies of water that are called "seas" are not actually seas; there are also some seas that are not called "seas". The following is an incomplete list of such potentially confusing names.
- The Sea of Galilee is a small freshwater lake with a natural outlet, which is properly called Lake Tiberias or Lake Kinneret on modern Israeli maps, but its original name remains in use.
- The Sea of Cortés is more commonly known as the Gulf of California.
- The Persian Gulf is a sea.
- The Dead Sea is actually a lake, as is the Caspian Sea.
- See also Extraterrestrial liquid water
Lunar maria are vast basaltic plains on the Moon that were thought to be bodies of water by early astronomers, who referred to them as "seas".
Liquid water may have existed on the surface of Mars in the distant past, and several basins on Mars have been proposed as dry sea beds. The largest is Vastitas Borealis; others include Hellas Planitia and Argyre Planitia.
Liquid water is thought to be present under the surface of several moons, most notably Europa.
Liquid hydrocarbons are thought to be present on the surface of Titan, though it may be more accurate to describe them as "lakes" rather than "seas".