Very fun and polished little game! The music is lovely and the art style is very detailed and gorgeous. I love the introduction of so many distinct biomes in a relatively short game, although it feels like some parts have a bit of unnecessary empty space. The attack animation of the player seems a bit out of sync with the sound and actual damage, and the actual range of the attack seems bigger than the visual indication - not too bad, but still confusing.
I think one complaint I have is that while the art and music sell the underwater setting very well, the powerups are basically typical Metroidvania fare. I think it'd be cool if the powerups were also "water-themed" instead of the usual double-jump and dash (and the light ability which is basically a keycard in disguise), though I don't know how exactly that could be done, either! I'm also not sure if I quite agree on the minimalist aspect, as the art style and gameplay don't really come across as "limited" beyond what's typical of gamejam games.
Regardless, it's an enjoyable game that definitely has potential for more!