Editor's note: John Thomason is an associate editor at our sister publication, Boca magazine, where he writes about the arts, entertainment and film. We share his film reviews.

What’s it like to be a man lost at sea? I mean, really lost–without the possibility of radio contact, no ships in sight for hundreds of miles in every direction, adrift in nothingness?

That’s the question posed in J.C. Chandor’s “All Is Lost,” a nearly wordless nautical vehicle for Robert Redford, who is onscreen 100 percent of the time, sharing the frame only with his boat, a life raft and the Indian Ocean.

The film couldn’t be a more marked departure from Chandor’s impressive debut, the talky Wall Street dramatization “Margin Call.” With a script built entirely on the actions of one man, “All is Lost” is an unforgiving study of survival and an exercise in Pure Cinema. In both movies, characters need to get out of jams in a constrained period of time, but that’s about the only similarity.

Eschewing any notion of back story, Chandor’s movie is set in the perpetual present; there is no past and ostensibly no future for his character. Redford’s nameless protagonist is an accomplished seaman, but that’s all we know about this rugged cipher. We don’t know if he’s leaving family back home, or his purpose out on those waters. I hesitate to even call him a character; maybe he’s just Robert Redford, escaping the bustle of agents, and scripts and interviews and the upcoming Sundance film fest and being Robert Redford for a much-needed solo respite on calm waters. Until everything goes wrong.

It starts with a hole in the hull. Water pours into his cabin, disrupting his sleep. And it keeps coming. Redford is a steady hand; he doesn’t panic, so neither do we. For a while, he manages to be a maritime MacGuyver, using whatever tools he has to patch the hole. But it doesn’t last long, and when a storm comes, his ship capsizes. The monster is at the gate of the castle, which is crumbling more and more with every passing minute. Trying to stop the flood is like trying to stop air with a shield.

All electronic devices are soaked or otherwise inoperable, leaving Redford with only a sextant, and he bobs through shark-infested waters using a map, his wiles and the sounds of silence. Would that there were at least a Bengal tiger or two to keep him company.

Compared to “All Is Lost,” “Life of Pi” and “Cast Away” begin to look like ever-more commercial survival stories, filled with concessions that provide comfort for the audience. In “Pi,” there’s the voice-over narration, the postcard visuals and the inherent reminder that our hero will make it out alive; in “Cast Away,” Robert Zemeckis tempers his character’s hopelessness with plenty of dialogue and absurdist humor. There are no such escapes in “All is Lost,” which is closer to “Gravity” in its purity and minimalism.

All is Lost” is a staggering accomplishment for both director and star. Chandor nobly refuses to sentimentalize or prove a macro view of his character’s milieu; we’re just there, with him, the entire way, tilting when the boat tilts, swaying this way and that in seasick camera acrobatics. And for the 77-year-old Redford to take a role this demanding, it’s almost guaranteed that he’ll take home his third Oscar next year.

Yet, by the time the final credits appeared onscreen, I walked out of the theater feeling surprisingly hollow, like I just watched a magnificent horse lead a race for an entire derby only to stumble across the finish line. It’s still the winner, but it closes with its weakest step, putting the film’s credibility at stake.

But why punish the good for the sake of the perfect? This is a movie that will be remembered for as long as movies are watched and studied, and that’s a pretty high honor.

All Is Lost opens in theaters Friday October 25.