I'm the girl & you're the guy.
Do you mind starting?
A boy has lived near the ocean practically his whole life. Maybe he's a fisher or a surfer or something..? But, one day, he's walking along the shore near his house and he finds a girl. He takes the unconscious girl back to his house, wondering if she's dead. Well, this girl wakes up. And she's surely not dead. In fact, she barely knows what most of the things are in the house. She keeps poking at her legs as if their foreign objects. She seems a bit...strange. Turns out, this girl is a mermaid. Poor thing ran away from home...