On terrestrial planets (such as Earth) the surface (whether ocean or land) is always clearly distinct from the atmosphere. On gas giants such as Uranus, this is not the case: they have a gradient density surface. This means that as you approach their upper atmosphere, you encounter gas which gets progressively thicker as you go deeper, until you're in a fog so dense it is practically a liquid. And from there the liquid gets thicker, like a thickshake I guess, until the pressure crushes your spacecraft. At no point could you say "I'm on the surface".
So liquid, maybe; ocean, no.