This was a super cool game! it had a nice gameplay loop and the upgrades definitely helped giving a feeling of progression and reason to keep diving!
One minor thing i think could of made the gameplay feel a bit more interesting would be some extra kinds of obstacles. with most of it being rocks they tend to blend together whereas if you used some other coloured objects it may have been a bit more interesting to dissern and more pleasant to look at.
otherwise great game, really fun with nice art and gameplay!