I was hoping to play a section involving having the mermaid tail lol, but nonetheless, I love the art, especially the character design.
I think having some music during the collecting would've contributed really nicely to the dreamscape atmosphere rather than only at the end when you've collected all the water.
As for the water vision mechanic, there wasn't any incentive, gameplay wise, to turn it off other than to just see the world. I think having some other mechanic to incentivize you to turn off your water vision would be good.
And as I stated before, the atmosphere and the character design really interests me, I kinda want to know what sort of world you had in mind for this game when you made it.