"The solar system is filled with invisible oceans trapped beneath frigid carapaces. And that’s forcing scientists to reconsider what they refer to as a habitable world... If these moons have (potentially) habitable—if not necessarily inhabited—oceans, then perhaps we shouldn’t consider Earth as the archetypal example of a life-supporting island in the cosmos. In fact, it may be a rarity, with these oceanic moons being the norm."
Link: https://www.atlasobscura.com/articles/space-oceans-outer-planets-moon