Man, I really wish the jam had a rating for presentation/art style because I absolutely loved what you went with. Very nostalgic of old school horror shooters like Resident Evil one. I wasn't a huge fan of the AD turning and semi-fixed camera but that makes a ton of sense since you were going for that style of nostalgic game. I also had issues with the game not always locking on to the sharks (especially the larger ones) but that did not prevent me from making it to the end of the game.
I really love the use of oxygen in this game though, had to be one of my favorite aspects. The concept of choosing between preserving your breathing capacity and getting to fire the gun is a great risk/reward and it fit the setting perfectly too. The only mechanic I wasn't 100% sure on was the flashlight as it was pretty easy to see without it. I wasn't sure if it made sharks more likely to attack so I ended up spending most of the game with it turned off. Overall, the game is fantastic and it was a really complete experience despite the short time frame of the jam. Excellent job!