I figure it's been long enough to justify a second post.
How hard would it be to allow swimming? basically just walking into water, if the water is supposed to be extremely cold ending the turn in it would cause stun, possibly a lot, if you kneel in water, basically diving, you take stun at the end of the turn. Visibility would probably go down, more so if you dive, but you'd be pretty hard to find both ways. Suits that would logically be heated could be immune to the cold damage, and those that have an air supply could be immune to the diving damage. Mostly it just seems odd that the gals can't swim in shallow water.