The art looks good and everything seems pretty well polished, but I feel like something's missing with this one. You're going down to get money so you can go down farther, but the only reason to go down farther is to...get more money so you can get upgrades to go down farther? Maybe it would help if the player had some kind of larger objective (e.g. he knows that there's something at the bottom of the ocean, and he's trying to make his way down there)? It just feels a little aimless right now.