Okay so now for MY suggestions.
First thing I noticed was that you don't SEE the water being pulled from the air. It just APPEARS and then you have regeneration. I suggest having Water particles (the same ones you have) swirling around you, growing in number until they reach your body. Then they can hover around your body and "heal" you. This is just an animation update I'd recommend. Do some more research on how you can apply math to get the right "swirls." You could even have the amount increase as the water gets closer to your body.
Second, you don't HAVE to hold shift, and I don't like. You should have it to where if the player releases shift DURING the mending and DURING the regeneration, then everything is canceled. Right now you just tap shift and BAM you have regen. Idk if you WANT it like this but I think it'd be less OP if you had to sit there and regenerate; similarly to Healing Waters.
I love your concept though. Being able to heal with the side-effect of getting hunger (representing getting "tired"). If you add the charge effect, you may even decide if you NEED the hunger. I think it's a clever feature so I'd say to keep it. However, it's really for what you had in mind for the move. If it's in an arena, chances are hunger is disabled. But if you want it aimed towards both Survival And Arena I think it's fine.