Duncan (Liam James) is an awkward teen who must spend the summer at a beach house with his mother (Toni Collette), her boyfriend, Trent (Steve Carell), and Trent's obnoxious daughter. Trent can't resist badgering Duncan, so the youth steals away to a water park and gets a job that will help him stay off Trent's radar. As Duncan tends to the slides and pools of the aging park, he finds a father figure in wisecracking park manager Owen (Sam Rockwell) at a time when he desperately needs one.