The sentries yelled, but Percy knew they couldn’t get a clear shot. They’d end up killing Frank. The other kids drew swords and got ready to charge into the water, but they’d be too late.
There was only one way.
Percy thrust out his hands. An intense tugging sensation fil ed his gut, and the Tiber obeyed his will. The river surged. Whirlpools formed on either side of Frank. Giant watery hands erupted from the stream, copying Percy’s movements. The giant hands grabbed the gorgons, who dropped Frank in surprise. Then the hands lifted the squawking monsters in a liquid vise grip.
Percy heard the other kids yelping and backing away, but he stayed focused on his task. He made a smashing gesture with his fists, and the giant hands plunged the gorgons into the Tiber. The monsters hit bottom and broke into dust. Glittering clouds of gorgon essence struggled to re-form, but the river pulled them apart like a blender. Soon every trace of the gorgons was swept downstream. The whirlpools vanished, and the current returned to normal.

The Son of Neptune, Chapter II