Does anyone know if you can buy an underwater casing for the 20D and if so, is it safe to use. Have heard stories of cameras coming up wet when the casing has got water in it.
There are quite a few different brands of underwater camera housings
Ikelite, Sea & Sea, Aquatica to name just a couple - they are fairly specialist items for digital SLRs and can be quite expensive - more than the camera - many digicam manufacturers also make them specifically for particular cameras - canon make lots of them for example - checkout the bhphoto.com catalog they list many.
maybe someone can comment if they have specific experience with the 20D - there are some underwater photography forums maybe try and track them down and ask there as well.
as for leaking - most will leak if you don't look after the o-rings properly - that is grease them and make sure crud doesn't build up - i had a nikonos for years and it never leaked but i looked after it
