I haven't played this genre of games before, but it was fun! On my winning run, I was already at 1 HP around 5 minutes in, and had to get all the water shield upgrades to heal back, lol.
The runs are pretty long, and I felt like the game was getting easier as I leveled up. Maybe the game could be shorter, or there could be bosses to shake things up (I know the jam deadline is the reason for the lower enemy variety, but I feel like the game could be a bit shorter in that case).
Also, the hitboxes are kind of off and there should be more visual/audio feedback for taking damage and losing shields.
I like all the upgrades and they were easy to understand, which is super important for a game jam entry imo.