I agree with everything he says, with the exception of the out gassing of the hammer on the Ruger pistol. He said it came from the firing pin striking the primer.....problem is, the out gas came directly where the hammer strikes the back of the firing pin, and not where the firing pin hits the primer, which is about 3" away.
On the revolver, the hammer strikes the primer directly, but not so on the semi-auto.
Common mis-nomer that you can't fire a weapon under water. Doesn't mean I would try it myself...but it can be done. The problem arises when you bring the weapon back above the surface of the water, and try to fire it when it still has water in the action, and/or barrel. Underwater the pressure all around the action and the barrel would be equal, however once taken out of the water this wouldn't be so, if there was still water in the barrel when it was fired.