Only 1 Planet has a habitable Ocean in our Solar System, Earth.
Many scientists believe that outside of our Solar System in an unknown galaxy we could find another planet with an Ocean, and possibly even one that could sustain life.
But as for right now the only known planet in the Galaxy’s with a habitable Ocean is Mother Earth.
some good reading on this topic can be found here:
Protect the Oceans, for all that live on this Planet.