OK! Europa, Ganymede & Callisto likely have subsurface liquid water, but...
...what about another possible celestial candidate that has been overlooked:
Saturn's moon, ENCELADUS.
[I hope I spelled it right.]
Anyways Look at those 22-year-old
images from Voyager-2!
You see in those images that the moon, Enceladus, has a large area that's basically level [smoothed over] and "crater free".
OK! OK! ALMOST crater free.
But Enceladus, like Europa, may
have a subsurface ocean...The idea should not be dismissed outright.
Jacob