Where I grew up in Maine was just far enough from the ocean that having a meaningful relationship with it meant renting a cottage at Old Orchard Beach. To a boy, there’s nothing as magical as the combination of Atlantic breezes, the beach and an amusement park. I had the sense on those trips that life couldn’t get much better. So I’m curious when I come across a movie about a young person for whom that seaside scenario somehow represents adolescence at its most vexing.

A movie like The Way, Way Back, a keeper in the coming-of-age canon. Liam James gives an expertly calibrated performance as disenchanted 14-year-old Duncan. The opening succeeds in explaining how a kid could dread a summer on the coast. His father has bailed, his mother is serious about the guy behind the wheel, and — even though he’s played by Steve Carell — that new man in both their lives, Trent, is a dick.

Eyes stern in the rearview, Trent adopts a parental tone to ask how Duncan would rate himself on a scale of one to 10. The women — Trent’s teenage daughter (Zoe Levin) and Duncan’s mother (Toni Collette) — are asleep. Would he ask if they were awake? Taken aback, Duncan guesses “a six,” only to be corrected: “I think you’re a three.” Trent, at whose vacation home Duncan will have to survive the summer, pretends to motivate, but he clearly has nothing in mind beyond fish-in-a-barrel bullying.

The film marks the directorial debut of Nat Faxon and Jim Rash, Oscar winners for their adaptation of The Descendants. Their friendship is a pretty good story in itself. The two met as members of LA’s Groundlings 15 years ago and have navigated the shark-infested waters of show biz using the buddy system. A writing team specializing in domestic dramedy, both are also actors. They make highly entertaining appearances here.

What Faxon and Rash do unusually well in their scripts is capture the way grown-ups and children occupy parallel universes that can intersect to profoundly comic — or comically profound — effect. Duncan wearies of watching Trent, his mother and their summer friends (Rob Corddry, Amanda Peet and Allison Janney at their boozy best) behave like they’re on spring break. He escapes to a park called Water Wizz (real place, real name) where he finally encounters a grown-up he can relate to.

That’s because Owen (Sam Rockwell at his best, period) is a classic specimen of that movie species, the cool guy suspended between youth and adulthood. Think Bill Murray in Meatballs. Sensing that the boy is struggling to fit in, Owen takes Duncan under his wing. It’s the beginning not only of a beautiful friendship but of a series of offbeat, touching character studies — and, natch, of the summer that’ll change Duncan’s life.

Faxon and Rash don’t reinvent the teen wheel here, just give it a fresh spin. We know where things are headed but enjoy the ride anyway, because we’re in such great company and capable hands. Carell does the against-type thing and scores his strongest performance in years. The dialogue is never showy, but it's always spectacular, and Rockwell proves there isn’t a nut he can’t crack.

His character is irresponsible, damaged, good-hearted and just force-of-nature funny. Which may be why Maya Rudolph, as his exasperated girlfriend, resists running for her life.

A movie’s got a lot going on when Rudolph barely squeaks into a review’s final paragraph. This one is well worth 103 minutes of your summer. It’s a moving bit of business about a boy learning the secret to making life a day at the beach, and the best work yet from two guys who really do go way, way back.