I agree with you about Antartica, but I think the pressure underwater at even quite shallow depths makes it harder to build any large-scale inhabitance there than on any of the bodies in this solar system that we'd want to go to, which have (I think) lower atmospheric pressure than earth. Of course, resupplying an oceanic habitat is much easier than resupplying anything off-planet, but besides that, I wouldn't be surprised at all if we have space colonies well before oceanic colonies.
