it is a known rule that merfolk aren't allowed to interact with humans at all. And humans absolutely can't know about merfolk. But one day, Percy, the merman prince of the ocean, sees a certain surfer girl on the beach, and instantly falls in love. He watches her every time she is in the water or at the beach

Percy: she's... Amazing... Beautiful.. And an amazing swimmer and surfer...

Percy's thoughts: I wish I could talk to her