I put an older G1 in an Ikelite SLR housing works great! I demo a G7...it maybe the best compact camera for U/W use. Great manual controls, one of the last cameras with a hotshoe, large LCD screen and 10mp.
I'am looking for a used unit just to have for land use. Maybe buy a G7 housing from Canon before the run out and wait for a deal on the G7, I hear that the G6 housing are already harder to find these days.
The Canon housing as is looks pretty good because what looks to be a built in dome port.