Ammo questions...
It was always my understanding that using a handgun underwater necessitated usng fmj ammo due to the water having a stronger hydrstatic effect on expansion of hollowpoint rounds. Considering most people carry aggressive jhp's for deffensive carry, would those expansion forces be enough to expand the bullet before it left the barrel possibly damaging the firearm and potenially causing other damage? something to think about...

As an aside, glocks have an optional fluted firing pin cup for firing underwater. Most people don't have an 'operational' need for this.