ack in the mists of 1973, it seemed a pretty novel idea for an anthropologist to place 11 demographically diverse strangers on a bare-bones raft for 100 days, and task them with crossing the Atlantic Ocean as tempers flare and sexual sparks fly between them. 45 years later, the so-called Acali Experiment sounds like a tired premise for the reality-TV machine’s umpteenth rejig of the “Big Brother” formula. The surprisingly short leap from radical academic study to lurid exploitation is navigated with wit, sensitivity and rueful social awareness in Swedish director Marcus Lindeen’s gripping debut feature “The Raft.”

Winner of the top documentary prize at Copenhagen’s CPHOX festival, the film deftly mines the tension between perspectives past and present, playing the contemporary reflections of the Acali Experiment’s surviving subjects — most of them women — against the defensive, ethically questionable observations of the project’s late Spanish-Mexican founder Santiago Genoves. Spiky, still-topical surges of cultural, racial and gender conflict emerge in the inadvertent dialogue between them, as well as in the live, present-day conversation between the reunited seafarers. Good-humored but needfully incisive, the resulting inquiry should engage viewers who remember the tabloid headlines generated by the Experiment as well as younger generations of social progressives — making for plain sailing (not to mention smooth selling) on the festival circuit.

“Peace on earth” is Genoves’ reply when one of his aggravated shipmates asks him what he hopes to achieve with this elaborate undertaking. Yet the more “The Raft” reveals about his motivations almost from the horse’s mouth, with extracts from the anthropologist’s journals delivered in voiceover by actor Daniel Gimenez Cacho — the more disingenuous that answer sounds from an academic interested in studying human conflict — only to flail and meddle when it doesn’t develop along the lines he expects. A literal motley crew ranging from aimless American waitress Mary to assertive Swedish mariner Maria to retiring Japanese photographer Eisuke, the 11 subjects were selected by Genoves as if he were casting a reality show, expecting specific formulations of sexual chemistry and personal friction.

That the voyage does not proceed at all according to the script in his head is not surprising; what is, however, is the fact that an actual scholar of human behavior imagined he could control the situation to this extent. Lindeen tracks the fallout from two vantage points. Genoves’ increasingly fretful version of events is delivered linearly, and in the present tense, giving the film a firm, tense narrative spine. His account, however, is persistently tilted, questioned and reframed by the reminiscences of the survivors, whom Lindeen assembles on a life-size studio replica of the original raft. (“The Raft” is a consistently polished affair, but special mention should go to production designer Simone Grau Roney.)

Those respective memories are, of course, further fraught with difference and disagreement. Some take a forgiving view of the project’s intentions, while others harbor complicated feelings of resentment toward Genoves, accusing him of gross exploitation and prejudice. His seemingly liberal motion to recruit women for the most powerful positions on board (none more so than Maria, appointed the raft’s captain with fractious consequences) is given particularly rigorous scrutiny — not surprising, given that all six female crew members are present for Lindeen’s summit, with only one surviving man (the still-reticent Eisuke) to join them.

The ensuing discussion runs compellingly high on passion and low on consensus. Was Genoves deliberately stoking a battle of the sexes, and was there a misogynistic undertow to his manipulation? There certainly was to the mainstream media’s bug-eyed coverage of the Experiment, which latched onto catchy phrases like “sex raft” and milked them for all they were dubiously worth. “No one’s writing about the science,” Genoves complains; again, you’d think

That Genoves, who passed away in 2013, is not present to defend himself at this heated reunion is not quite the drawback you’d expect. Edited by Alexandra Strauss and Dominika Daubenbuchel with a keen ear for the rhythm and flow of debate — whether within a group or a conflicted individual — “The Raft” brings his appraisal and the crew’s long-delayed inquiry to separate but parallel points of regret and uncertainty. All can agree that mistakes were made, if not which ones; what that says about the success or otherwise of the Acali Experiment is for the viewer to ponder.