Love underwater submarine games! :)
I think the consistent submarine sound could be lowered quite a bit. Sounds more like I'm in a rocket taking off than a submarine underwater, but that's a nitpick.
Not sure if it was just me, but moving my mouse didn't seem to do anything? Was a bit difficult to navigate around.
Nice work with the different guns. Wish I had something to shoot at, though! Nice touch also with the rear camera. That's a nice detail.
Kind of made me think of The Outer Wilds but underwater instead of in space. I liked the bubbles effect you had going on. With some points of interest to explore and things to shoot at, this could make a good game!