This Web site goes into great deal about the Europan ocean
It wasn't just guesswork or "faith" that has determined what is under
Europa's ice crust:
http://www.math.washington.edu/~greenber/EuropaHistory.html
If the ice crust is thin enough, as is becoming more accepted, we may
not have to send a cryobot down through the ice to get samples of the
global ocean. We may even find creatures dead and alive in the ice
itself. Perhaps even some circling Jupiter blasted off Europa from space
impacts.
