[GreyOwl]

Or even simpler, "Fire Ant Mound must always be placed either on or adjacent to a land space." No need to mention water at all

EDIT: Of course, it also doesn't make sense to place it on molten lava. Maybe it should always be placed on a land space, period, just to keep it simple. That way they can still cross water, but if they want to end up in it, they'll just have to walk like everyone else.