I love the audio in this game. The sound effects are crisp, and it just feels great to kill fish and collect money.
You also get extra gameplay points for trying to do something new with the idea of it getting darker as you go deeper. I don't think I've played a game that does that.
This game did confuse me slightly when I started it. The very first thing it told me to do is "Press Z," and I complied. This brought me into the store to purchase things. I hadn't yet moved around or shot at things, so I had no idea why I would be purchasing stuff right away.
I think this would be better if you introduce the store later on, perhaps after the player's first successful deep sea run.