Underwater is a term describing the realm below the surface of water where the water exists in a natural feature such as an ocean, sea, lake, pond, or river. Three quarters of the planet Earth is covered by water. A majority of the planet's solid surface is abyssal plain, at depths between 4000 and 5500 m (13,000 to 18,000 ft) below the surface of the oceans. The solid surface location on the planet closest to the center of the orb is the Challenger Deep, located in the Mariana Trench at a depth of 10,924 m (35,838 ft) under the sea.

underwater - growing or remaining under water; "viewing subaqueous fauna from a glass-bottomed boat"; "submerged leaves"