The confirmed liquid water in the Solar System outside Earth is 25-50 times the volume of Earth’s water (1.3 billion cubic kilometers). The locations of subsurface oceans are on Europa, Enceladus, Ganymede, Titan, Ceres, Callisto, Dione and Pluto.
There also could be subsurface oceans at Rhea, Titania, Oberon, Triton, Orcus, MakeMake, Eris, 2007 OR10, and Sedna.
At 1122 km (697 mi) in diameter, Dione is the 15th largest moon in the Solar System, and is more massive than all known moons smaller than itself combined. About two thirds of Dione’s mass is water ice, and the remaining is a dense core, probably silicate rock.
Callisto is the second-largest moon of Jupiter, after Ganymede. It is the third-largest moon in the Solar System and the largest object in the Solar System, Callisto may have a small silicate core and possibly a subsurface ocean of liquid water at depths greater than 100 km.