Percabeth Honeymoon: The Sea Battle

Piper's POV:

Percy and Annabeth are having their honeymoon now. I'm really happy for them, they've been through a lot together, even before i met them. I've heard stories about them going on quests and saving Olympus before i was introduced any of these. I'm really glad they are still there for each other.
I was in my cabin packing my stuff to stay organised, then all of a sudden an iris-message popped up. It was Annabeth. I was expecting to see Percy too, but he wasn't there.
"Hi," I said cheerfully,
"Hey Piper," Annabeth tried to smile, but i could tell something's up, she wasn't too happy.
"What's wrong, Annabeth?"
"I uh.....It's nothing.....but.....So here's the story, Percy and I were at the beach today. When i got back from the washroom, i saw Percy standing on the waves with a girl. The girl wears sea shells and a sea blue dress and stuff, i think she have something to do with the sea gods or spirits whatever. And after that, Percy seemed upset all day and wouldn't talk, he said everything was fine, but i doubt that. Is something wrong at Camp, Piper? Please tell me," Annabeth looked really concern and worried.
"Everything's fine at Camp, really. Not much has happened." I answered honestly.
She frowned, "Really? Then what's wrong with Percy? We were having a great honeymoon, but after he talked with that sea girl, his mood and everything changed."
"Hmm....Sea girl.....i'll keep an eye on things at Camp and try to research for some sea girl." I tried to make Annabeth cheer up a little, but she still seemed upset.
I'm totally clueless, like Annabeth. Who is that sea girl? Why does Percy seemed upset after seeing that sea girl? Nothing comes in mind, but i'm gonna find out. I hope thinks will get better.

Notes