Sam Rockwell isn’t likely one of the first names that come to mind when asked the question of great current actors. Despite a resume filled with roles in box office hits ("Iron Man 2"), Oscar bait ("Frost/Nixon," "Conviction"), cult darlings ("Moon") and everything in between, the usually antsy performer has never quite been able to make the leap from solid actor to viable star.

He could have years ago. Rockwell was actually on the short list of actors to play Iron Man before a troubled but slicker and more polished actor named Robert Downey Jr. managed to convince Marvel he would snag an audience. The rest is history. Downey Jr. went on to claim a monopoly on cocky, smartass heroes; Rockwell went on to play a side villain in the much-derided sequel. Life is cruel sometimes.

It’s too bad because Rockwell has enough engaging charisma and on-screen energy to power five lesser supposed "stars." He served as the uncontrollable sparkplug of chaos in last year’s "Seven Psychopaths," and he now plays a similar burst of life in the warm growing-up tale "The Way, Way Back," one more smartly contained yet still undeniably electric.

Before Rockwell and the rest of his water park misfits show up, however, it’s choppy waters for "The Way, Way Back." Liam James (TV’s "The Killing" and "Psych") stars as Duncan, a relentlessly mopey 14-year-old going on vacation to a beach house with his distant mother (the freakishly natural Toni Collette), her pushy jerk of a boyfriend Trent (Steve Carell, decently playing against type) and Trent’s snitty daughter (Zoe Levin).

The car ride up is uncomfortable (Trent pesters Duncan about becoming more social, cruelly rating him a "three out of ten" to get his point across), and things don’t get much better when they finally reach their destination. The parents – greeted by an amusingly drunken Allison Janney – have fun drinking, smoking and lounging, while Duncan struggles to connect with anyone, despite the attempts of Janney’s cute, equally bored daughter (AnnaSophia Robb).

Part of Duncan’s issue with connecting might be the fact that, as played early on by James, he’s a glum, tedious, wet beach towel of a character.

To be fair, I’ve always been an extrovert so it’s possible I simply have a harder time relating to such a blocked-in personality. Even so, James doesn’t bring enough across, either in terms of performance or personality, to make me relate. He just seems like another typical sullen, indie coming-of-age kid with the moodiness cranked way up.

Worse yet, first-time directors Nat Faxon and Jim Rash (Alexander Payne’s Oscar-winning co-writers of "The Descendants") seems to be following his lead. The film’s early pacing and editing is awkward, and the blandly shot scenes just inertly patter on. There’s a part of me that thinks the first act’s stiffness is purposeful, to put the audience into Duncan’s uncomfortable mindset, but if so it doesn’t work. An intentionally clumsy movie still plays like a clumsy movie, just with higher pretensions.

Duncan eventually meanders his way to a job at Water Wizz, a low-budget neighborhood water park run by Rockwell’s man-child Owen and his exasperated partner (Maya Rudolph, charming in a poorly defined role). With a gentle push from Owen and his fellow goofy employees – including Rash and Faxon themselves – Duncan slowly opens up, earning the nickname Pop ‘n’ Lock for intervening on the most congenial dance mob in history and learning the secrets to oogling bikini-clad patrons without getting caught.

It’s not a particularly unique turn for "The Way, Way Back." Even so, as Duncan begins to loosen up amongst his quirky comrades, so does the film. Faxon and Rash seem to get more comfortable behind the camera, lightly mixing the comedy and the family drama into a winning blend.  

The side characters are a hilarious hoot without devolving into cliché piles of excessive quirk, and though his evolution is more "finally!" than truly rewarding, I did warm up to James by the end. As the role requires more of him than sad eyes and slouched posturing, he becomes a far more engaging and convincing character.

Then there’s Rockwell, who snatches the audience’s attention – and more than a handful of laughs – every time he hits the screen. He adds a lot of life, as well as a good bit of weight and humanity, to the usual indie movie mentor role while still making it feel refreshingly effortless. Like a lightning strike to a swimming pool, his contagious charge can’t help but electrify the rest of the film.

"The Way, Way Back" may start dramatically damp, but it ends giving off a bright buzz.