So as stupid things go this seems like a no brainer but to my surprise you can actually fire guns underwater and here is the video to prove it.
Firearm aficionado Andrew Tuohy gave it a go with a .40 Glock 22 in his own pool. The video above was shot with Pentax WG-2 on the “high speed” video setting. It’s been slowed down to 30fps for an added bad ass factor. (Watch for the bullet and casing to slow down and sink to the bottom at the end.)