Hi All

Planet-sized water globs have been studied mathematically, but usually as a mix of volatiles - like water with some methane, ammonia etc. To retain water against gravity at liquid water temperatures would require an escape velocity 5 times the RMS velocity of gaseous water at the ocean's temperature - else it escapes into space. Ocean-sized is too small to be stable, unless it's frozen.

The minimum size for a liquid water glob is a radius of 4300 km at 300 K - that's a big "ocean". Actually below a certain depth it freezes into high-pressure ice, even at high temperatures and the density increases with pressure, so the glob will be a bit smaller due to higher density deep down.

Adam