Imagine a pipsqueak version of “Baywatch” melded with the syrupy nostalgia of “The Wonder Years” and you’ll have some idea of what “Age of Summer” is like. Bill Kiely’s coming-of-age-on-the-sand story is rambling and episodic, and it takes the lessons learned by its pint-sized protagonist all too seriously, but it’s innocuously good-natured and nicely shot, so one can’t be overly hard on it.

Set at California’s Hermosa Beach near Los Angeles in 1986, the movie focuses on the experiences of a kid nicknamed Minnesota (Percy Hynes White, looking a lot smaller than he does on the current Fox program “The Gifted”) though he is actually a recent transplant from Chicago. He and his equally puny best friend Woods (Jake Ryan) have been accepted into the junior lifeguard program, a group of recruits whom a formidable figure named Tony (Diarmaid Murtagh) presides over in the demanding manner of a US Army drill sergeant.

While Tony puts Minnesota, Woods and the other youngsters through their paces on sand and sea, our hapless little hero is distracted by the disappearance of his prize possession, a BMX bike. Searching for it involves him with a couple of ne’er-do-wells nicknamed Pots (Kane Ritchotte) and Pans (Mcabe Gregg), who promise him information about its location if he’ll steal a marijuana plant from the pad of a hedonistic, near naked oddball called The Yizz (Brian Van Holt). When he does so—in a raucous, daytime theft—they point him toward a sort of local shaman called The Rock God (Peter Stormare) for advice.

Minnesota is also feeling the first pangs of teen rebellion, tasting his introductory beer and showing a greater interest in girls than Woods, who’s still into more juvenile pursuits. So he eagerly embraces the stash of magazines some of his beach buddies have hidden in a restroom, and aims to catch the eye of Brooke (Charlotte Sabina), a beautiful blonde. His interest in her also draws him more deeply into the big mystery of the summer—the disappearance of a surfer. That matter bookends the picture: at the start, posters are being put up asking for information about him, and at the end, his whereabouts are revealed, part of the process of Minnesota’s maturation.

Gaining new friends and interests, of course, also entails leaving other things behind, and “Age of Summer” doesn’t ignore that. One casualty is Minnesota’s friendship with Woods, which at first seemed so central but by the close is pretty much gone. And another is that bicycle. The last shot suggests that what was once so important has become, in view of all that’s happened, a mere afterthought.

Gawky little White, who can register pain more easily than joy, makes an agreeable if hardly scene-stealing hero, and Ryan is a convincing nebbish. Sabina certainly fills her pinup-ready role well, and the other youngsters register decently in their intermittent turns. Among the adults Van Holt comes off worst, rampaging around like an even crazier version of Zach Galifianakis, but Stormare brings an air of stoic calm to the proceedings in his cameo. Best of all is Murtagh, who pulls off Tony’s cartoonish bombast but by the end has also revealed the heart behind it.

One of the pleasures of the movie is the cinematography of Darin Moran, which captures the crystalline brilliance of the beach and the ocean, giving the location the paradisiacal aura that the nostalgia-suffused tale demands. On the other hand, the pervasive narration is so flat, and so flatly delivered, that it saps some of the enjoyment from the images.

“Age of Summer” is far too bland to be at all memorable, but it’s a harmless growing-up-on-the-beach tale that families can watch together, though it would be more at home on a kids’ cable channel than in a theatre.