I'm looking for a book that I remember from fifth or sixth grade. That means published 1981-83. It was about two kids in the backwoods, maybe the Smokey Mountain area. I think maybe the girl is staying with her grandmother and the boy lives there. He seems to teach her the ways of the back woods. I remember there was skinny-dipping in the book. I think maybe the boy's name was Rusty? And that the author's name was two initials and then a last name.