If movie trailers are an accurate depiction of contemporary American life, then males are never more hilariously awkward than in their virginal mid-teens, and females never more so than when they are in their mid-30s, single, and coping with an impending marriage of a younger sister.  Movie previews a year from now will tell us so, five years from now, and onward. Perhaps those are the audiences Hollywood is trying to attract. Or perhaps those are the painful years audiences of all ages empathize with. For the purposes of this review, let’s deal with the boys.  The thirty-somethings and forty-somethings are having a blast in “The Way Way Back,” an amiable drama-comedy about a 14-year-old dealing with mom’s boorish boyfriend and the pretty, perfectly age-appropriate blondie one house down the street.

Said street is spectacular to look at in a New England-y way, and as one of the wiser supporting characters points out, “there’s a beach in your backyard.” It’s a stretch of summer homes where for a few weeks everyone knows each other, tans together, drinks beers together, and possibly more shenanigans. The new boyfriend (Steve Carell) has a family place in that spot, and as the group drives toward their intended destination he asks the awkward boy, Duncan, to rate himself from 1-10. The poor kid (Liam James) begrudgingly plays along and says he’s a 6. Carell’s character, the smarmiest guy he’s ever played, retorts with “I think you’re a 3.”

That exchange, uttered from the angle of a rear-view mirror, sets the tone for the teen: Get on board, or be left behind. He chooses left behind. While everyone else is enjoying boat trips and margaritas in the first half of the film, Duncan sort of bounces and drifts like tumbleweed from the beach to the breakfast table to the street to the dinner table. The girl next door (AnnaSophia Robb, from “The Carrie Diaries”) understands those sad eyes and mopey posture better than most, given her own broken home experiences, and so he admits to her he wants to live with his father, now building a life in San Diego. Alas, the boyfriend inevitably reveals at a boozy beach party the ugly truth — that daddy doesn’t want him.  This all transpires on lovely summer evenings, and I wondered if anyone else ever noticed that when movie characters are talking profoundly near the ocean there’s never any wind.

Act 1 is very afterschool special, but the filmmakers had a weapon stashed away for Act 2: a water park filmed lovingly at the real-life Water Wizz Park in Wareham, the gateway town to Cape Cod. Here Duncan meets the Sam Rockwell character, Owen, who is a half-assed manager to a funky crew of park employees. Duncan is promptly hired and finds a place for himself.

Rockwell is known for chewing up every frame of the scenery, and he’s perfect as the guy who looks so cool during the touristy season, all the while hiding the hardships of living in a tourist town in winter with that same humor. Better, he even admits to Duncan what happens to the cool townie when winter hits -– a confession you rarely catch in actual life.  His girlfriend, a co-worker played by former “Saturday Night Live” star Maya Rudolph, drills a few classic lines herself.

But Rockwell and Rudolph are only bystanders to the best moment in “Back:” when Duncan must convince some park goers to stop dancing at the water park for money (think the performers at NYC’s Washington Square Park). Something unexpected occurs — instead of the dancers grousing about it, they ask the kid to show them his own moves, and miracle of miracles, Duncan obliges and the crowd slurps it up. With help Duncan finishes with a breakdance head-spin (lensed terrifically from an upside-down angle, so we feel it), and afterward, amidst the applause, our boy relaxes his shoulders and smiles. So does the movie.

At this point the main character (and the audience) doesn’t want to bike back home, but he must because there’s a worried mother in the mix, played by Toni Collette. She’s underused a bit but still outstanding. Like in “Little Miss Sunshine”, Collette is a natural around the dinner and living room tables, and adds some extra seasoning to throwaway lines like “dinner’s almost ready.” I had no problem with Carell and Collette as a couple here after they played brother and sister in “Sunshine,” because these are completely different personalities with almost-terminal problems in their relationship. As the son’s spirits lift, the mother’s mood sags.

But like mothers do, how can she stay low for long when her kid finally seems so happy? In the finale the young lead looked like an otter, his t-shirt soaking wet, his face sun-kissed and pleasant. This is as it should be during a vacation stay: Enjoy it all and make a big splash at the end of the waterslide. One of the directors, Nat Faxon, is from the area and plays a lifeguard in the picture. Maybe he was a lifeguard there for real at 14, or a spot someplace nearby.   Faxon and his co-director, Jim Rash (who has a funny part as well, as a park employee who sells swim trunks), were coming off an Oscar win for adapted screenplay for the surf-and-sand drama “The Descendants,” and probably had a credit line to make one personal picture. Maybe “Back,” shot in Faxon’s old backyard, was that passion play. If so, he made a movie with a PG-13 pitch just right to watch on a rainy day in a beach town.

Indeed, some conversations on summer nights, where the weathered wood of a porch meets the sand, stick with you forever.  Back in the summer of 2010, at the end of a Fourth of July weekend, I drove through Wareham — again, the setting of the movie — to visit a street where I spent my own vacations over 20 years earlier.  When I stepped out of the car the locals happily came out to greet me. This wasn’t a surprise — they were friendly to me as a kid, after all. But what I didn’t expect was how they anticipated my arrival. They explained that summer after summer, July after July, once-young visitors came back older and grayer, sometimes with their own kids, if only for a long moment. The neighborhood has been inviting my generation back for years. It was just my turn. Put that in a movie trailer.