You cannot use magic underwater at 0 Air, which basically silences you.
Viewing post in bug? couldnt cast magic unless I recalled first
I had air. I had 700 or so in fact. I was simply locked out of magic unnecessarily. (C'mon I was up to the Hydra, I clearly know the game!) I was using a wind slimes ability to exist, I was completely prepped to fight the Hydra.
The only interaction I can tell you I did differently is that it was the first time I had used the rune that restores 100 willpower.