Rubbish. You have no idea what a 480 can do underwater. If he wants a 480, whats the problem? Not everyone is soley obsessed with bang for buck. Maybe like me the op has had a very good experience with nvidia, and that counts for something. Heat is the only issue IMO and sticking it underwater will sort that.
+1
And to say a 5870 will beat a 480 under water is just foolish.