https://youtu.be/6lG-snJZIV8
FYI: the barrel extension on the Glock is there to keep the diver from getting a hydrostatic shock. The dense water carries the shock wave a lot better than air, so that extension does ‘silence’ it for the diver.
There’s a nearby video that talks about how they made their underwater nosie suppressor. Shooting a gun underwater is literally dangerously loud - water doesn’t compress or expand like air, so it sounds like the gun went off right next to your ear. So they made a custom suppressor to fire it safely.
Mandatory breakdown, freshwater bath and oiling after each hunt.