“Atlantide” is the Italian name for Atlantis, the fictional island utopia imagined by Plato, supposedly cursed by the gods and swallowed by the sea. It’s a pointed legend to evoke in a film about Venice, the sinking city that, real as it is, feels like a place we collectively dreamed into being, that could somehow be taken from us at any moment. The crumbling fragility of this impossible city and the defiant ennui of its native sons are both richly illustrated in Italian video artist Yuri Ancarani’s dazzling hybrid documentary, which navigates Venice’s various secondary islands and the waterways that separate them through the heavy-lidded eyes of young men who live for rollicking motorboat action and, it seems, not much else. All life here is made to feel as beautiful and vulnerable as the city itself.

Since premiering at (where else?) Venice last year, “Atlantide” has made a strong impression on the festival circuit, buoyed by its ripe, sensual imagery and seductive sonics. The film’s woozy audiovisual splendor doubles down on everything that “The Challenge,” Ancarani’s similarly well-traveled 2016 debut feature, suggested about his gifts as a stylist and an observer of milieu: As in that film’s transfixingly beautiful, bizarre depiction of the moneyed Qatar falconry scene, “Atlantide” magnifies and aestheticizes a peculiar, socially vibrant subculture to such a degree that it bypasses vérité altogether en route to a kind of earthy surrealism. As a character study, however, the film remains distant and opaque, even as it fictionalizes the trajectory of its real-life human subjects. Perhaps granting us greater access to their inner lives would break its humid, hypnotic spell.

The tone is set by an enchanting opening credit sequence, centered on a group of youths swimming and diving off a little-frequented vaporetto (or water-bus) stop on the sleepy island of Sant’Erasmo — floating between Murano and the Lido to the east of Venice proper, but less romantically celebrated than either of those beauty spots. To the propulsive accompaniment of a throbbing electronic score, the teens jump into the water, resurface and repeat the process in a languid loop of lazy pleasure, Ancarani’s camera picking out the sensory specifics of tan lines and damp towels. This is the Venetian summer some way removed from the flocking tourists on the main island. The lagoon at once outlines the confined world of Sant’Erasmo locals and provides them with a sprawling playground of temporary escape.

For 24-year-old Daniele — a surly, taciturn wastrel who serves as the film’s human focal point — life is only worth living on the water, ideally at great speed. He’s one of numerous young men in the region who can only be described as the Venetian equivalent of boy racers, with barchini (souped-up motorboats) standing in for a slick set of wheels. Anyone who has been on a lumbering Venice vaporetto will have noticed these kids zooming across the water in foamy, curving circuits, going nowhere fast and then some, for the sheer, heart-quickening joy of it. Daniele’s life on dry land seems nothing to write home about: we’re given but a brief glimpse of his humdrum job on an artichoke farm, while his conversations with girlfriend Maila betray little passion or intense emotional investment.

Rather, his life’s pursuit is simply to build the speediest barchino possible. In this regard, he joins a reckless cult of similarly oriented young men, whose macho exploits Ancarani shoots with a strutting, sweating verve that recalls nothing so much as the first “Fast and Furious” film — particularly in rapturous scenes of their nighttime gatherings, where garish fluorescent lights further bedazzle their breakneck slicing of the waves. Yet there’s no real sense of family here, just of testosterone-fueled competition: Daniele, in particular, isolates himself from his peers, devoting himself to his boat with a single-minded ferocity that can’t lead anywhere good.

Departing from strict documentary form, Ancarani contrives a melodramatic arc for him that rather highlights how little we know of the smaller, more mundane details of his life. The camera’s attention sporadically drifts to other handsomely heedless guys in his orbit, about whom we learn even less. Only in one remarkable scene depicting an exchange between Maila and her manicurist — their faces never seen as their weary, revealing conversation plays out over shots of busy, beautified hands — does “Atlantide’s” gorgeous sociology really get under its participants’ sun-beaten skin.

That detachment is by design, however, paying off in an extended, stunningly abstract finale, in which humans recede from the frame altogether. Aboard a jaunty-paced boat, the camera stares out like a gawking traveler, tilting to its side so that the rosy-lit architecture of Venice and its reflection in the choppy waters fuse into one morphing kaleidoscope of doily-like symmetry. Venice will outlast its wild-hearted denizens, “Atlantide” suggests, before the whole city, like Atlantis before it, succumbs to the sea.