Gameplaywise it's not a 5 stars game, but I think the dev will be able to tweak it enough to make it more enjoyable to play, the game loop is correct, it's just too easy and too fast. It could really be a 20 hours game if you plan it correctly, add some self-doubt to the character/diver, some more mechanics related to hull tension maybe. What really shines in this game is the writting, the descrpition of the fauna, the solitude and darkness. It's really good! You should really make a slower gameplay so your text can shine.