[quote=Goldmarble]
Then explain how a firearm can operate under water?Don't believe me?Don't understand? The Propellant contains all the oxygen needed to fire. So yes. You can fire a gun under water, and you can fire a firearm in space.
[/quote]

While it may be water proof it may not be air proof, being underwater is significantly different to being in a vacuum with no atmosphere at all, and all the air will likely be sucked out and dissipate into nothing.