“The Way, Way Back”: The downward slide of adolescence

“The Way, Way Back” opens Friday at Sundance Cinemas. PG-13, 1:42, three stars out of four.

I had the darnedest time early on trying to figure out when “The Way, Way Back” was set. The cars, the clothes, and the soundtrack definitely pointed to the debut feature from writer-directors Nat Faxon and Jim Rash as being set in the ’80s. But then smartphones and contemporary slang would creep in. Was this film set in the present day, or did it have the world’s least attentive production designer?

In fact, “The Way, Way Back” is set in the here and now, but my confusion is somewhat understandable. The adult characters in the film, all on summer vacation on Cape Cod, are pining for their irresponsible teenage years, which happened to occur during the Reagan Administration. And the kids are living through their own version of a bittersweet ’80s John Hughes-style dramedy — Rash even based some of the more painful moments on his own adolescence back in the ’80s.

But that sort of nostalgic referencing isn’t a bad thing, as long as you try and live up to the movies you’re paying homage to. And “The Way, Way Back” turns out to be fresh and alive, embedding its feel-good comic tone in characters and situations that feel real, sometimes painfully so.

Liam James is 14-year-old Duncan, who is a model of teenage awkwardness; he carries himself like his arms and legs just sprouted the night before, and he isn’t quite sure what to do with them. He’s been dragged along to Cape Cod by his mother (Toni Collette) and her new boyfriend Trent Ramsey (Steve Carell). Carell plays pretty beautifully against type as a bullying, Type-A sort who is always on Duncan’s case, but able to say just the right things to his mom to keep her around. Honestly, Carell is more despicable in this movie than he is in “Despicable Me 2.”

The vacation is clearly a chance for the parents to get drunk and party on the beach with their friends (including Rob Corddry and Amanda Peet as neighbors, and Allison Janney as a boozy divorced mom) while their teenaged children seethe on the sidelines. Seriously, is there anything more horrifying for a teenager than to see their parents partying? “Way Back” captures that discomfort acutely.

Retreating into himself, Duncan explores the town and finds a water park called Water Wizz that has been immaculately preserved since it opened in — you guessed it — the 1980s. Owen, the loopy manager of the park (Sam Rockwell), takes Duncan under his Hawaiian-shirted wing, and offers him a job. At the park, Duncan makes his own set of friends (including Rash and Faxon, their faces familiar from their TV work on “Community” and “Ben & Kate,” respectively) and slowly gains confidence in himself.

“Way Back” is good-natured, and just true enough about the painful humiliations that can mark the teenage years, so that when Duncan’s inevitable triumphs come, they feel satisfyingly well-earned. Unlike the charmingly cute “nerds” of most teen movies, James’ Duncan is authentically dorky and off-putting at times, and he develops a warm chemistry with Rockwell’s zinger-dropping goofball that’s clearly patterned after the Bill Murray-Chris Makepeace relationship in “Meatballs.” Rockwell is just perfect as the layabout goofball who keeps a fatherly concern beneath the surface of his zinger-a-minute patter.

My only concern here is that the water parks at Wisconsin Dells will use “The Way, Way Back” to entice Slovakian kids to come work there during the summer. (Kids, it’s just a movie! Sam Rockwell isn’t really going to become your friend!)