Liked the art style. Controls and goal are pretty intuitive.
One thing that keeps bothering me is that the fish takes a while to spawn when I get to certain depth. Even on some places that I passed through, the fishes spawned are already de-spawned when I get back there. That really slowed the game down a lot.
Also the game over criteria is a bit too harsh, one mistake and all efforts are gone. Pretty devastating especially in later stage. I'd prefer that when the characterran out of oxygen, it respawn on top of the ice with the fishes and money gone. Less punishing that way. Unless the roguelike approach is what you want to achieve, if so ignore this suggestion.