I think I made a character once who was an amoeba, but I removed her due to her being redesign and changed from main protagonist to a side character in the story she was supposed to be a part of.

Maybe you could take perks from her.

First, make rain heal her instead, slimes shouldn't be hurt by water when their bodies are 95% water.

Make her freeze quickly instead, having slower movespeed when her tempurature is below a certain level, maybe even art assets of her looking more frozen and crystalized.
The cold is a slime's actual weakness.

Also have her deal and take less damage.

I think my old character was voiced by a hydraulophone too, I might still have those sound files if you'd want to use them.