Just got a Canon Underwater Housing for G11
Have not used the housing. I was going to buy a G11 with the housing. After research I opted for the Panasonic TS-2 that is built as an underwater camera/P&S. Years ago I used the canon A-1 P&S film camera and it worked fine, but was designed as an underwater or above from the outset.
What I read regardless of large housing size is that you have to be very careful to take care and protect the seals and clean them from debis which is obvious, I know. Any error and it is at the bottom of the sea.
Hope all works ok and be sure to follow the directions to keep the housing integrity.