OMG, when I read this I thought you were talking about the kind of "housing" one LIVES IN! Like an underwater habitat :lol:. My hubby could build you one of those... You just have to pay for the materials and a couple tickets to the Bahamas
Scooty, the link is to a review of a few waterproof digital cameras, pocket camera sized. The most popular is the Olympus Stylus 790SW. They're only good for 10 feet, but Krish is scared of the ocean for the most part, anyway.
The problem is underwater housings for the XT/XTi will cost more than the camera. Unless you're going to get serious about it, it's actually a lot cheaper to go with a point-n-shoot digital with underwater housing. Additionally, anything deeper than 10' is going to require some pretty serious lighting. The on board flash just won't cut it down there.