Cute little game!
The controls are a bit slow, but that's expected in a game about a submarine ^^. The graphics are nice, but I would have enjoyed a couple of sounds to add to the atmosphere.
I think I went everywhere, but I couldn't find a way to lose HP... I don't know if it's a bug or if I missed enemies? Also, do the game has an ending? I collected a thousand fish but nothing happened, so I stopped playing, did I miss anything?
Overall, it's a chill and cosy game. I would have liked a clear objective and some sounds, but I enjoyed the little time I spent on it. Congratulations =)