DOes anyone have a link to the guy off AR15.com who broke his AR underwater?
Also, Glocks and HK's have been known to fire underwated but ALL AIR NEEDS TO BE REMOVED from the barrel etc. It could be done with rifles but is a lot harder because of the smaller barrel diameter, longer barrel length. Also the higher velocities make it more dangerous.
Also, submerge your head when you are doing it and you fire there go your eardrums.
Thats what we were told in Scuba Diving class. 
