Canon WP-DC23 Waterproof Case for Canon Powershot SD770IS Digital Cameras

Used it to scuba in Australia. It went as low as 60 feet without any problems. Canon also sells weights for this housing to achieve neutral bouyancy so the camera won't float while you scuba. I didn't buy them and really don't feel that it is necessary. The camera wasn't floating like a balloon in the saltwater. It might be slightly buoyant in salt water but not that bad.

For the SD770IS with the attached WP-DC23 housing Canon says you would need one weight to achieve neutral buoyancy.

I used this unit on a dive trip to Grand Cayman. I was hesitant, to say the least, concerning jumping into the ocean with a new camera. However, it worked great. I had no issues (other than running out of memory). A pro photographer was in my group and he had an expensive custom housing/camcorder rig and was never able to get it to work. I recommend this highly for its simplicity and (relative) low-cost/small size. Note: The housing has an optional weight that can be attached to overcome its default positive buoyancy. I'm still not sure whether this is a good idea: trade a minor hassle of the housing getting in the way from time to time vs. losing it into the depths if it becomes detached. 2nd note: I would suggest practicing with the camera to get a feel for the housing's exterior controls before going into the water.