love this game, how you die gives you direction to evolve is a very good idea and you use it in a smart way! I really enjoyed the game!
Some nitpicks are the O2 bar, it is quite hard to notice it, I die in the boss level to realize you need to jump and get O2 before drown. I would suggest (maybe) reduce hp when you are out of O2 instead of killed directly, or add the water in an early stage in the boss fight, otherwise, it is a little frustrated that you need to redo the boss fight while the boss has only left 20% hp.
Overall I like this game, I'm a bad platformer player so I didn't get all map explored but it still one of the best games I played in this jam! I'd like to see it gets into a full game since the mechanic is very unique and has potential. say if you die more times in swim you get a longer O2 bar, or jump higher if you are impaled more times, these evolve is not needed if you are good at the game, but might give some bad players(like me) motivation to keep playing it.