I liked the art, but there were a lot of things that stuck out and made it hard to keep my attention. Since you're new to programming, I recommend you keep practicing and learning. With experience in pixel art, I can see you making some solid jam games in the future.
Some things to keep in mind for the future
- Feedback to the player - A player wants to know if they're doing something successfully (or unsuccessfully). If I'm attacking something, I want to know that my hits are confirming or if I'm being hit for example. Not only is it helpful to the player, but it can be satisfying as well. So in this case, sound and visual effect really come into play here. I'd argue that, for game jams, having that is more important than having music.
- Camera placement - in any kind of platformer, you want to make sure the player can see enough around them so they can assess where obstacles/platforms/enemies are at. Player's don't like making "leaps of faith" because they can't see anything below them that they have to drop/jump to.
- Guiding the player - You want to make sure that the player doesn't spend time trying to figure out your basic mechanics. If you have something that isn't immediately clear, you need to convey the information in some kind of way. Like when you get an unlock, it's nice to have something that tells you what you unlocked, what it's main function is, and maybe a little hint at what it could also do that may be part of a puzzle down the road. In your game, I had no clue what was going on with the attack/jump. If i was in water, I shot projectiles, but out of water, I could jump. However, I had no idea how that mechanic was going to be used.
These are just a couple pieces of advice that immediately come to mind. If you keep this kind of feedback in mind, you'll get better at this. Congrats on submitting, though! I hope you keep working on developing your skills!