It’s the season for solitary survival stories at the movies. There was a time when James Franco had things pretty much to himself in “127 Hours,” but recently Sandra Bullock has made the box office hum by being marooned in space in “Gravity,” and now Robert Redford is a yachtsman left adrift in the middle of the Indian ocean in “All is Lost.” The only prospect worse, one might quip, would be watching any of these films alone in a theatre auditorium.

Actually, as cinematic exercises each is a quality product. But despite its location on the open sea and far less virtuosic direction from J.C. Chandor than Danny Boyle’s, “All is Lost,” anchored by an admirably restrained performance from Redford, is more akin to the confinement of “Hours” than the broad outer-space vistas of “Gravity.” It’s been rightly described as minimalist filmmaking, which begins with its only extended dialogue sequence—a voice-over read regretfully by Redford as his unnamed character pens a farewell note to his family and friends after coming to terms with the fact that he’s unlikely to survive much longer, drifting in a battered rubber life raft without any more food or drinkable water.

The film then skips back to when the man’s boat, the Virginia Jean, was intact and he was going about his solo crossing of the ocean with professional skill. Awakening one morning, he finds his cabin floor drenched in water, and when he investigates he finds that a huge shipping container, which has presumably fallen from a cargo ship, has rammed into his yacht, spilling some of its cargo—sneakers—into the sea and, more importantly, leaving a gaping hole in the hull. The camera follows him as he pries the metal crate from his boat and then uses whatever materials are at hand to patch up the damage as best he can.

But, of course, the ad hoc repairs prove insufficient, especially when bad weather comes up and the yacht is tossed around by enormous waves. With the radio out and the navigational system equally dead, the man does everything he can to keep the boat afloat and preserve whatever supplies he can. Ultimately, though, he’s forced to abandon the craft for the flimsy life boat, all the while employing whatever skills he has to pilot himself into the shipping lanes, where he hopes to be noticed by a passing vessel and rescued.

Throughout the earlier portion of his ordeal the man strives to maintain his normal patterns as much as possible—shaving, having regular meals and the like—just to keep going. And he shows himself supremely resilient and remarkably composed, going about his tasks with an attitude that remains quietly resolute, even hopeful, until all actually seems lost. After a few desperate, apparently futile, attempts to attract the attention of somebody on the vast barges he spies in the distance, carrying the same sorts of boxes as the one that wrecked his boat, he gives in to the inevitable—or is it? That leads to a final sequence that’s deliberately ambiguous, involving a light that can be taken in a variety of ways, any of which seems just a bit of a cop-out. (“Gravity” suffered from a similar reluctance to take matters to their natural conclusion.)

Still, until that final steeping back from the brink, “All Is Lost” is a survival story that eschews melodramatic exaggeration in favor of a straightforward approach that extends to Redford’s understated yet authoritative performance. With a very limited number of lines to deliver—largely confined to be a few choice expletives after that opening monologue—he conveys the character’s changes with subtle shifts of expression, and makes us believe in the man despite the fact that we’re given absolutely no back story on him. This is, after all, an existential piece, in which only the “now,” and the decisions and actions taken in it, matter.

Chandor keeps a firm but not unyielding hand on the rudder, refusing to lapse into cliché or sentiment. Cinematographer Frank G. DeMarco complements that approach with work that emphasizes an almost tactile sense of reality, though the visuals opt for a more poetic touch when associate cinematographer Peter Zuccarini takes the camera underwater for shots of sharks circling the life raft or the man swimming for dear life. Pete Beaudreau’s editing sometimes feels a bit sluggish, and Alex Ebert’s score can get a mite blowsy, but these are minor defects.

You have to admire the authentic texture of “All Is Lost,” even in the few scenes filmed in tanks. But that comes not merely from the technical expertise of the filmmakers but from the naturalism of Redford’s performance. He handles the physical demands of the part splendidly—and they’re considerable—but what’s most impressive is how he maintains the character’s stoicism without it becoming simply dull. Perhaps that’s partially the result of our familiarity with the actor—he’s practically a member of the family, after all. Without an ounce of showy overindulgence he brings a gentle dignity to this “Old Man and the Sea” tale—though the story itself is as much Sartre as Hemingway.