Water trapped Romans

Very slowly, using only two fingers, Annabeth drew her dagger. Instead of dropping it, she tossed it as far as she could into the water.

Octavian made a squeaking sound. "What was that for? I didn't say toss it! That could've been evidence. Or spoils of war!"
Annabeth tried for a dumb-blonde smile, like: Oh, silly me. Nobody who knew her would have been fooled. But Octavian seemed to buy it. He huffed in exasperation.
"You other two..." He pointed his blade at Hazel and Piper. "Put your weapons on the dock. No funny bus — "
All around the Romans, Charleston Harbor erupted like a Las Vegas fountain putting on a show. When the wall of seawater subsided, the three Romans were in the bay, spluttering and frantically trying to stay afloat in their armor. Percy stood on the dock, holding Annabeth's dagger.
"You dropped this," he said, totally poker-faced.

Down in the water, Octavian yelled, "Get me out of here! I'll kill you!"
"Tempting," Percy called down.
"What?" Octavian shouted. He was holding on to one of his guards, who was having trouble keeping them both afloat.
"Nothing!" Percy shouted back. "Let's go, guys."
Hazel frowned. "We can't let them drown, can we?"
"They won't," Percy promised. "I've got the water circulating around their feet. As soon as we're out of range, I'll spit them ashore."

MoA ch.19