The boy has a 'wet dream', where he's a knight rescuing the teen girl, who's been tied up with tarnished clothes and her breasts exposed. As the boy unties her and starts to hug her semi-naked body, he wakes up. Realising he's had a wet dream he punishes himself by slapping his penis with a wet towel.
There is a skinny dipping scene at beginning of film where one boy has rear nudity. There is also frontal and rear nudity of two boys and a girl diving or jumping into river.
Frank (Tobias Raue, 15) spies on couples cuddling by the side of a lake through binoculars. He then takes his trunks off and jumps into the water naked, with brief side and full rear nudity.