Neat game! Certainly see the Iron Lung inspiration, as others have mentioned.
It felt hard to know how to feed the fish at first. It felt like the movement of the sub was inconsistent, or atleast moved a lot more with the left/right buttons than forward/backward.
I don't know if I softlocked myself, but I got to day 3 and it said to Resurface so I was. Then I was torpedoing fish for ages with nothing changing.