Briar Coats and the tunnel of styx
Briar is a wild boy. Living in a mangrove-tree city, he has been assigned the job of builder, but he is desperate to become an explorer.
At least he can swim in the lake for solace—that is, until he realizes that he can breathe underwater!
There he meets Verity, a person who looks like him, but she has a long flowing tail and a green glow. Verity helps Briar learn the truth about his father’s disappearance, and helps him change the underwater world of Naraka for the better.