It wasn't uncommon for your boyfriend to knock on the window next to your bunk, trying to wake you up so he could take you down to the lake.
Percy liked the water for multiple reasons, being the son of Poseidon being a big one. He likes to go for swims to clear his head, to think think, and it's even saved his life a couple times.
One his favorite things though, was how easy it was to hide in.
Percy positioned himself in the thick of the seaweed, using the tangle and dark to his advantage. He could see you, looking all pretty and unsuspecting, while you couldn't see him, ever so handsome and ever so scheming.
He could hear your scream from under the water, air bubbles leaving his mouth as he laughs.
"Gotcha," the son of Poseidon grins, wiping the water off his face as he rejoined you on the surface after pulling your leg (literally.) You'd think after the first ten times you'd get used to it.