Great game, I'm a big fan of Subnautica and this is clearly a 2D clone, but that's a great thing! You have got great graphics and gameplay here, very atmospheric with good sound effects too. If I could give you the following constructive feedback:
(1) please add a save function or at the very least a pause - I had to close my game after my lunchbreak!
(2) there was a bug where some sharklings chased me up close to the surface then they seemed to be frozen in place. When I went back down deep enough they just jumped back there.
(3) make the first few crystals spawn close to the player. I was blasting plants and scenery for a while wondering why I wasn't making any money.
(4) rename the 'shop' since it's not really a shop, or is it? This is a bit of a deviation from Subnautica here.
Overall great game, really enjoyed it, how long have you been working on it?