Mean Creek (2004)

When Sam Merrick is beaten up by local bully George Tooney, Sam's older brother Rocky and his friends Clyde and Marty plan to pretend it's Sam's birthday to "invite" George on a boat trip in which they would dare him to strip naked, jump in the lake, and run home naked. But when Sam, his girlfriend Millie, Rocky, and Clyde see George as not much of a bad guy, they want to call off the plan, but Marty refuses. Will the plan go ahead as planned?