The Battle of the Labyrinth (Percy Jackson and the Olympians, #4)

by Rick Riordan

Annabeth glared at me like she was going to punch me. And then she did something that surprised me even more. She kissed me. “Be careful, Seaweed Brain.” She put on her hat and vanished. I probably would’ve sat there for the rest of the day, staring at the lava and trying to remember what my name was, but the sea demons jarred me back to reality.

The boat smacked her in her face and she went down with the ship.