He concentrated, and fire flickered over his fingers. For a split second, Leo was excited, because he hadn’t expected it to work underwater. Then his plan started working a little too well. Fire raced up his arm and over his body until he was completely shrouded in a thin veil of flame. He tried to breathe, but he was inhaling pure heat.
“Leo!” Frank flailed backward like he was falling off a bar stool. Instead of racing to Leo’s aid, he hugged the wall to get as far away as possible.

The Mark of Athena, Chapter XXIII