Why isn’t Joe Swanberg doing a TV show? I say this without intending the slightest dis whatsoever. Swanberg’s improv-heavy, character-driven stories, done quickly, seem to be perfect for the new Golden Age of television. I would so watch “Drinking Buddies” every Sunday night on Showtime.

His latest, “Digging for Fire,” is a lightly-plotted and organic film about a marriage in — not crisis, exactly, but stasis. Tim (Jake Johnson) is a public-school teacher missing his adolescence, while RoseMarie DeWitt is Lee, yoga instructor to the stars in Los Angeles. They have a young son, played by Swanberg’s real-life son Jude, so their adult lives have subsumed to his needs. Jude was also in “Happy Christmas,” so I’m expecting that over the next dozen years, Swanberg’s output will also be his “Boyhood.”

One of Lee’s celebrity clients has asked her to housesit for a few weeks, so the family moves into this incredible mansion, with a pool, huge living room, and a woodsy hillside path. While idly digging through the dirt on the hill, Tim finds a rusty revolver, and a bone that sort of looks like a human tibia.

Tim is fascinated; are their more bones under the hill? Has he uncovered evidence of an unsolved murder? Lee urges him to forget about it, since it’s, you know, not their hill. But when she heads off for a weekend away, Lee invites a few friends over to help him dig. Soon, they’re having their own Hardy Boys adventure in the backyard — albeit, with more alcohol and blow than Franklin W. Dixon ever put in his books.

Things at the house take sort of a dark turn when one of Tim’s less reputable friends (Sam Rockwell) stops by with a couple of women (Brie Larson and Anna Kendrick) who may or may not be prostitutes. Meanwhile, Lee’s own weekend takes a turn when she finds herself hanging out with hunky restaurateur Orlando Bloom.

The whole hill thing is a glaringly obvious metaphor for Lee and Tim’s marriage, and the dangers of digging too deep into what’s really bothering them about their relationship. And, at its heart, there’s not much in “Digging for Fire” that’s exactly revelatory — marriage is hard, kids suck up a lot of your time, and you shouldn’t invite your friend’s cocaine dealer to your wife’s client’s house.

But Swanberg has an almost ridiculously good cast to work with, and they seem to revel in the chance to ease into his improvisational approach (no wonder actors like Kendrick and Johnson keep coming back). DeWitt, in particular, who has worked in a similar style with writer-director Lynn Shelton, really gets the chance to show what a present and subtle actress she is.

Some have complained that nothing really happens in “Digging for Fire,” and there are no obvious stakes. Well, yeah. But just like that hill full of bones, it’s what’s going on under the surface that matters.