The game looks really nice, one thing i think that you could add in order to sell that deap sea feeling a bit more is by adding some ambient "dust" particles. I have also made a game that takes place deep in the ocean and i feel that these particles really add some nice detail
(if you dont quite get what i mean you could check the game out on my profile called hyperbaric)
(also i would reccomend watching the video that someone posted in the comments playing the game instead of playing it yourselves, it a shitshow of bad level + game desig and you will get lost