It’s common to think of adolescents as lumps of clay, unshaped by experience and a true sense of self, and easily molded by whatever forces make the deepest impression. But Nat Faxon and Jim Rash, the writer-director team behind The Way, Way Back, appear to have taken the “lump of clay” idea a bit too literally with their 14-year-old hero. Duncan (played by Liam James) spends half the movie wearing an expression somewhere between mopey and eerily absent, as if he’s gone beyond ordinary teenage malaise and half-checked out of consciousness altogether. The best he can manage is an a cappella mumbling of an REO Speedwagon song spilling out of his iPod, but among family and even sympathetic peers, it’s either monosyllabic answers or lights-out altogether. It would be one thing if Duncan were merely an unformed mass of quirks and emotions, but he’s such a blank that it’s a wonder why anyone takes an interest in him, the audience included.

The center doesn’t hold in The Way, Way Back, and neither does the bulk of the movie, a coming-of-age comedy-drama that’s part The Ice Storm, part The Graduate, and wholly workshopped to death. The title refers to the back-facing rear seat of an old-fashioned Buick station wagon that shuttles Duncan to summer-vacation hell. Rebounding from a divorce, Duncan’s mother Pam (Toni Collette) wants him to bond with her boyfriend Trent (Steve Carell) and Trent’s stuck-up daughter Katy (Ava Deluca-Verley), but Trent is an overbearing scold who tries too hard to assert himself as the boy’s new father. Girl-next-door Susanna (AnnaSophia Robb) sees something in this inarticulate blob of a kid, but Duncan doesn’t show any real signs of life until he meets Owen (Sam Rockwell), the goofball proprietor of a dilapidated water park named Water Wizz. When Duncan gets a job at the park, he finds a warm surrogate family to take him away from his dysfunctional real one.

Rockwell was given the latitude to turn Owen into an affable variation on the eccentric man-children he’s played from Box Of Moonlight to Seven Psychopaths, and he’s by far the best thing about The Way, Way Back—so good, in fact, that his splashtown fiefdom suggests another, much better movie. But Owen exists only insofar as he can help Duncan find his way, and that goes double for Susanna, who’s shown as smarter than the other girls primarily because she brings a book to the beach. They’re coming-of-aides, there to assist in Duncan’s emotional development, then ultimately choke on the exhaust as he peels away from them.

Faxon and Rash won an Oscar with Alexander Payne for adapting the screenplay for Payne’s The Descendants, but they don’t share Payne’s gift for evocative visual detail. Where The Descendants brought a rich sense of how ordinary Hawaiians go about their everyday lives in paradise, Faxon and Rash barely make it clear where The Way, Way Back takes place, other than some antiquated beach town that pipes in a lot of 1980s adult-contempo hits. John Bailey’s camera shrugs through a series of indifferently staged scenes that rely too heavily on a name cast and predictable dramatic beats to bring them sputtering to life. There’s a potentially compelling story here about children of divorce and the tentative ways they set about forging their own relationships, but the filmmaking is too rudimentary to draw it out subtly. Faxon and Rash cut Duncan a clear, broad path to growth and perspective, but the audience can see where it's going long before it gets there.