I really enjoyed this. Loved the PS1 aesthetics your went for, I could definitely imagine this being a horror classic if it was released back in the 90s! Reminds me of exploring the shipwreck levels in Tomb Raider 2. The audio logs were a nice touch too.
My only complaint is that the combat feels quite unresponsive, especially against the sharks who just keep coming at you. A short stun, or impact effect would make a big difference.
The underwater settings is really unique and suits the limited grid based movement. I wonder if you could add 90 degree turning up and down too to really disorient the player and add to the sense of unease and claustrophobia.
Overall, a really cool little horror game.