"I JUST NEED some time out of my life," Leigh (Kristen Bell) tells her parents. Leigh—who's 29 years and 10 months old, and not, she repeats, 30—has just arrived at her childhood home, having abruptly left behind her life in New York City. Leigh's informed her parents she'll be staying with them. Indefinitely. Because life in New York—where she writes stories for the Associated Press and is sleeping with a guy who's engaged to someone else—has simply become too much for her to handle. So Leigh, shrugging off questions about whether she's had a nervous breakdown or is depressed, reverts to her teen years, when she was an only child living at home, a virgin, and a valedictorian. She gets back her old job as the lifeguard at the neighborhood pool, and tracks down her old BFFs Mel (Mamie Gummer), who's now a high school vice principal, and Todd (Martin Starr), who's barely in the closet.

Leigh's soon living it up like a teenager, to the confusion of her mother (Amy Madigan) and to the boner-y delight of Little Jason (David Lambert), who's constantly hanging around the pool. Jason is 16, with ADD and a skateboard, and he's planning on dropping out of school and skipping town. It doesn't take long for Jason and Leigh to start hanging out, and it doesn't take long for Leigh to start giving him advice ("You are 16. You have your whole life ahead of you. You have no idea how lucky you are right now."), and it doesn't take long until Jason figures out the ridiculously hot woman in the red swimsuit and short jorts is pretty good at making terrible decisions. So it doesn't take long until they're boning, and not even trying to keep it a secret from Mel, or Todd, or Jason's dad, or any of the tiny screeching brats who run around the pool all day.

The Lifeguard is interesting for a couple of reasons, the first of which is watching another character learn that you can't ever go home again, no matter how shitty real life is. (It's a theme that's also riffed on, more insightfully and entertainingly, in Edgar Wright's The World's End, which came out last week.) But there's also Bell's strong performance—in a subtle shift into a character far less bubbly than the ones she played in Veronica Mars, Hit and Run, and a few forgettable romcoms, Bell manages to make what should be a profoundly unlikeable character something disconcertingly close to likeable.

But The Lifeguard is also uninteresting for a couple of reasons, the first of which is that, aside from its basic idea and Bell's performance, there isn't much here. Thanks to a soundtrack of painfully on-the-nose pop and the fact that nearly every shot looks like it was run through an Instagram filter, the overly long The Lifeguard starts to wear out its welcome—but when one realizes that the stories of those around Leigh are more interesting than hers, the film really stumbles. There's Mel, for example, who tries to ignore what's happening between Leigh and Jason even as she longs to escape from her own stressful life; or Leigh's mom, trying and failing to start a life of her own; or Jason, who hasn't just lucked into probably the best experience of his life but also has to contend with being an actual teenager, while his girlfriend's just pretending to be one. Somewhere in here, there's a great film, but this isn't it.