Ocean planet

An ocean planet (or ocean world, water world, aquaplanet or panthalassic planet) is a type of terrestrial planet that contains a high amount of water. This may be a planet with ocean covering all of its surface (except maybe at the polar regions, where ice caps may exist), or a planet with a ocean bellow its surface (called a subsurface ocean). 

Ocean planets are also the name of planets that have other types of liquids on them such as liquid ammonia, ethane, or even lava.

Habitation
A ocean planet covered in water may have conditions to support life.https://www.space.com/20728-new-alien-planets-oceans-life.html | What Might Alien Life Look Like on New 'Water World' Planets? | April 18, 2013 This has been questioned though, since some studies suggest that water worlds may not be friendly to life, since elements like phosphorus (a key part to DNA) may be hard to access, since it any be hidden in rocks at the bottom of the planet's oceans. Other problems here may be certain parts of the water cycle not working on an ocean planet, or the low amount of oxygen in the atmosphere.https://www.newscientist.com/article/2154137-ocean-covered-planets-may-not-be-the-places-to-search-for-life/ | Ocean-covered planets may not be the places to search for life | 21 November 2017 With that being said, there are still possibilities for life on water planets.

Possible ocean worlds
There are a few planets that could be ocean planets. All of these are extrasolar planets. 

Kepler-22b a rocky super-Earth that lies in the habitable zone of its host star. 
Gliese 1214b a super Earth that circles its red dwarf star very close, but a deep ocean may exist under high pressure caused by a strong atmosphere.
Kepler-62e, a rocky Earth-like planet that may be a warm and humid planet. 
At least one of the TRAPPIST-1 planets may be an ocean world. The TRAPPIST-1 system is home to at least seven Earth-sized planets. 

Several of the moons in the solar system may have oceans bellow their surfaces, which would make them ocean moons. One such example is Europa, one of Jupiter's moons. 

References

Category:Types of planet