Original theme. The art is cute and thematic. The sharks look nice and fierce! The music suits the tone and subject well.
The game could communicate more clearly with the player. Because I played the game a couple of times, I understand that collecting all the coins advances you to the next level, but this could have been conveyed more directly, e.g. with a little chime or a message. The first time I beat a stage, I thought I had lost (run out of oxygen?) and was restarting.