Thalassophobia

The Avatar, the Last Airbender, the bridge between two worlds...
That's Aang, a 112 year old boy who Katara accidentally found, frozen in a giant iceberg. When the ice had cracked open, a blazing beam of light had shot up into the sky like a mysterious signal. Her brother, Sokka, had been wary of it, but she had thought little of it.
Maybe she should have paid a bit more attention to it though, because her Gran Gran informed them the next day that the "young man" that she had found wasn't the only odd person who showed up that day.

Katara had many questions, but for now, she would stick to the one she had asked Aang just the day before.

"What's your name?"

"Percy. Percy Jackson."