An artist's conception of what the surface of an ocean planet.
Ocean planets are a type of planet whose surface is covered completely by water. The oceans would be hundreds of kilometers deep and at the bottom, water would become ice because of extreme pressure caused by the ocean water on top. 
An artist's conception of an ocean planet.
GJ 1214b is a recently discovered ocean planet that is ~42 Light-years away from Earth. 
- ↑ Ocean Planets on the Brink of Detection
- ↑ Link