So they find an island and cavort about with the pirate-looking crewman, named Paddy. Then Paddy dies.
Going years without the aid of civilisation, Em (the girl) nonetheless figures out that girls are supposed to faint at the sight of dead people, are supposed to wear makeup all the time (even if she hasn't got any), and are not supposed to ever get pimples.
Richard (the boy) figures out that boys are stoic and a little violent, they don't have facial hair yet at sixteen, and they masturbate.
It takes these poor morons forever to figure out how to have sex, but when they do, boy is it ever . . . a muddled, somewhat confusing montage that left me not feeling sure whether or not they'd actually had sex or just spent a while lightly kissing each other's shoulders. The film maker must've felt it needed to be made clear, so he included a shot at the end of the sequence of one sea turtle mounting another. I kid you not.
It's been about ten years since they were lost and now the boy's uncle, who must've sensed somehow that they'd been living comfortably on an island all this time, finally decides to come looking for them.
Apparently the movie was meant to be a kind of sex education film. Which is kinna funny.