Found this, looks like there is a 5D housing already out there:

The MediaSub BUW 1 KF 3 Digital underwater housing was already suitable for various Canon, Fujifilm, Nikon and Olympus digital SLRs, and is now also available for the EOS 5D.

The housing is made of carbon, has stainless steel, seawater resistant quick-clasps and provides access to all functions of the EOS 5D. Nikonos V compatible flash connection, handles and leak warning are included standard. Pricing for the BUW 1 KF 3 housing starts at 1620 euro.

That image doesn't come up in my browser. But I think that this link will help.
http://www.ikelite.com/web_pages/2d5canon.html

Alex

image urls says http://...kf3-20dbig.jpg

yes, seems to be a 5D housing anouncement on www.digifish.nl.
"KF3" is a standard Bruder housing type and is adapted for several camera models. I assume the picture doesn't actually show a 5D housing. I think it's a 20D housing pic.

Julian

According to Harald Hordosch of Seacam, they'll also have a housing for the 5D ready by January, in time for the BOOT expo.

Mat