Nor does the situation improve once the proto-family is ensconced at Trent's shingled cottage--the "Riptide"--on the New England shore. As a friend will later explain to Duncan, this environment is like "spring break for adults," a vacation from everyday life and its attendant disappointments. Pam is introduced to Trent's various summer-season friends (expertly played by Allison Janney, Amanda Peet, and Rob Corddry) and these putative grownups quickly get to work drinking--Bloody Marys for breakfast, wine at lunch, margaritas with dinner, and beer more or less constantly--experimenting with a little reefer, and generally behaving like adolescents freed from parental supervision.

Duncan, meanwhile--an actual adolescent freed from parental supervision--gets himself a job.

Fleeing the middle-aged debauch unfolding all around him, Duncan discovers a

frozen-in-time 1980s water park, whose offbeat manager, Owen (Sam Rockwell) takes a shine to the shy boy. Over the course of the summer, Duncan begins to gain a bit of wisdom and self-confidence, learning valuable lessons about--

Wait! Don't stop reading!

Yes, it is true that in its broad contours The Way Way Back could be mistaken for a tedious, coming-of-age message movie full of canned sentiment and idle uplift. But it's not. Written and directed by actors Nat Faxon and Jim Rash--who won an Oscar in 2011 for their adapted screenplay of The Descendants--the film is sharp, and tender, and extremely funny, with the kind of accessible-indie vibe that characterized such seasonal sleepers as Little Miss Sunshine and 500 Days of Summer. An unexpected yet irresistible cross between Meatballs and The Ice Storm, The Way Way Back just may be the best movie of the summer.

The cast is uniformly excellent, in particular Carell (neatly cast against type), Janney (deep in her comfort zone), and Maya Rudolph as Owen's charmingly beleaguered significant other. As Duncan, young Liam James may occasionally lean a bit heavily on the awkward-teen schtick, but his vulnerability is acute. And if his quasi-love interest, played by AnnaSophia Robb, falls into the too-good-to-be-true category (kind, smart, beautiful), well, that's more or less par for the course. But it's Rockwell's Owen--an overgrown boy in a movie full of regressing adults--who contributes most to the film's air of compassionate whimsy. If this role, one in a series of sneaky-good performances that Rockwell's been delivering for years, doesn't finally earn him the recognition he deserves, I'm not sure what will.

That said, The Way Way Back is, at its core, a deeply personal work on the part of writer-directors Faxon and Rash--who are also, it should be noted, very good in supporting roles. According to Rash, the opening scene, in which Duncan is forced to grade himself on a scale from one to 10, was taken verbatim from a conversation he had with his own stepfather. (He chose six, he says, because he didn't want to seem "conceited.") Indeed, though it's set in the present day, the movie is awash in nostalgia for childhoods that unfolded in the 1970s and '80s: the Buick station wagon; the lovingly dated water park; references to Bonnie Tyler, Mr. Mister, REO Speedwagon, Pac-Man, Toughskins jeans, and bikes with banana seats. Even beyond such nods, the movie is about summer vacation as a zone out of time. As Rash puts it, "We all evolve, but the place we go to in the summer remains the same."

The Way Way Back is a film of modest ambitions, but one that fulfills those ambitions exquisitely, from its opening frames to the pitch perfection of its very last shot. (Along the way, we're treated to what are almost certainly the best two scenes ever filmed on a water slide.) On a scale from one to 10, I'd give the movie an eight. But I'm grading low, lest anyone involved become conceited.