I love the style and the overall game is super cute. It's not too punishing and it's a great game for a jam.
Some things that could be improved are the following:
- Health gauge feels backwards. I am losing oxygen but the gauge is filling up. Also it's a bit hard to see as my focus is always on my cursor for aiming and it blends in with the water.
- The water animation felt off because it was not uniform with the overall pixel art style. If the water curves were also pixelated then it would have fit in a lot more.
Other than that it's fun and good job!