has part has part has_part composed primarily of liquid water planetary surface planet ocean planet While this planetary form is still mostly theoretical, strong candidates exist such as the extrasolar planet GJ 1214 b and ocean planet candidate Kepler-22b. A planet which has a surface layer that nearly completely or completely covered by water, and which has a substantial portion of its mass composed of water. aquaplanet panthalassic planet envoAstro water world An axiom to express that the planet has a 'substantial' proportion of its mass in the form of water wound enhance this class.