Overall, I like it a lot. The quick gameplay loop is addictive, the visuals are well done and the music tracks are perfect for underwater exploration. Big pluses for that splash screen at the start and the shipwreck. Very cool!
Some (hopefully) constructive feedback:
-I love that grabbing the money has a sound effect, it contributes to a sense of addictive replay. I would have liked to see a sound or animation or something when buying gear from the shop. Even a little sign that said "SOLD OUT," would have worked. Anything to reinforce that process with some kind of player feedback. On a related note, was cool to see the gear on the player avatar.
-From a system design standpoint: a little "breather" at the very start would be nice. Because you start with such little breath and you immediately begin drowning, on my very first play I died before I really knew what was happening. I could see something like this working: on-screen text that reads "Dive down to start!" and then the breath meter begins as soon as the player goes down.
Lovely overall, thanks for sharing!