It's rumored that there is water beneath the surface. In face NASA recently announced that there may have been water plumes spotted on Europa. This would be huge and would merit sending a probe.

It isn't rumored. If the conditions there are similar enough, then there is liquid under the ice, same as Lake Vostok (and other subglacial lakes) in Antarctica. I worked with glaciologist Igor Zotikov, who discovered it, and there are numerous calculations & evidence that show, that subglacial lakes are on Europa, and probably elsewhere.