Don't forget to add the alkaseltzer ...
"Subject: Put alka-seltzer in your water camera bag
When I made a hacked underwater camera housing to take video of the stingrays in the Caymans, I put two alka-seltzer in the bag with a weight and the camera. In case of a leak, the seltzer foams, blowing up the bag and making it more positively buoyant (probably also tends to expel the water). It worked too! You certainly notice when you get a leak ..."