Magic 5 Volume 1

With a triumphant expression, Suga threw a slash of lightning at the unmoving Shizuku.
"Shouha Suiren."
Shizuku tried to defend herself with a wall of water. How could water protect against lightning? Yet Shizuku's Noble Art blocked the powerful current without trouble.
"What!?"
「S-Somehow, lightning had no effect! Commentator Oreki-sensei, what's going on!?」
「*Cough cough* That's probably ultra-pure water….」
「Ultra-pure water?」
「Yeah… everyone thinks that water loses to electricity, right? But no, when water does so it's because impurities like ions and microbes in the water make it conductive. Water becomes less and less conductive as it becomes more and more pure, until it becomes ultra-pure and forms a complete insulator that electricity won't pass through.」
「I see… oh? Then why don't other water users copy this tactic?」
「It's not that they don't, they can't. Completely removing impurities at the ion level is like sifting gold dust from desert sand. Only Shizuku-san's level of magic control allows her to perform such a technique.