BEVERLY HILLS, CA -- OCTOBER 6, 2013: _Robert Redford is photographed at _L'Ermitage Hotel on October 6, 2013 in Beverly Hills. He stars in the upcoming film "All Is Lost." ( Liz O. Baylen / Los Angeles Times ) (Liz O. Baylen / Los Angeles Times)

Robert Redford was going down with the ship.

Yes, the character he plays in writer-director J.C. Chandor's "All Is Lost," which arrives in theaters Friday, is a lone traveler on the Indian Ocean whose sailboat is taking on water from a gash in its hull. But this water emergency wasn't in Chandor's screenplay.

Filming in the same massive outdoor tank that James Cameron used to make "Titanic" in Baja California, Chandor was shooting Redford inside the cramped quarters of the 39-foot Virginia Jean. The sailboat was half-submerged, with the actor and a skeletal crew sloshing through waist-deep water aboard the vessel, the script supervisor hiding in the boat's tiny head.

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Suddenly, an assistant director yelled: "Out of the boat! Out of the boat! Everybody, out of the boat!" The crew, toting its $500,000 digital camera, quickly climbed out. "But the assistant director doesn't say the boat is sinking," Redford recalled. "And then I thought, well, maybe I should get out, too."

The actor and his director scrambled out just a few seconds before the Virginia Jean scuttled in some 60 feet of water.

"Just to be clear, I was the last one off," Chandor, 39, said. "I really didn't want to be the guy who killed Robert Redford."

If making the rest of the movie wasn't always as dangerous, it certainly was arduous.

The physical production and its inherent corporal tests were just half the battle. Redford, 77, did more of his own stunts than he originally had intended. He said he permanently lost 60% of the hearing in one ear after high-pressure water was sprayed onto him to simulate a storm.

But far more challenging for Chandor was how to tell his story using only one actor and almost zero dialogue, without resorting to any of the tropes of the castaway genre.

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From the story's inception, Chandor decided he would resist using voice-over, flashbacks or a random piece of sporting-equipment-as-sounding-board to illuminate his character's back story, thoughts or emotions. Instead, action would be everything. It would be a total turnabout from his previous film, 2011's "Margin Call," a dialogue-heavy Wall Street thriller with an ensemble cast.

Just as Redford's sailor has to patch the fissure in his listing boat, the audience would have to fill in all of the story's expositional holes.

Redford initially feared that chasm would leave him as an actor as adrift as his solitary seaman. The "All the President's Men" and "Butch Cassidy and the Sundance Kid" veteran would pepper Chandor with questions about his character, who doesn't even have a name. Who is he? Where is he from? Does he have a family? Why is he on this trip? But Chandor wasn't sharing.

"He never really answered. He talked all around it. So you have to do a lot of deciphering," Redford said. "And I realized that, well, if that's where he's going that's fine with me. So I stopped asking."

"All Is Lost" starts with a letter, just as Chandor's writing of the movie did.

"I'm sorry. I know that means little at this point, but I am. I tried. I think you would all agree that I tried. To be true, to be strong, to be kind, to love, to be right. But I wasn't."

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Exactly what Our Man (as Redford's character is called in Chandor's screenplay) is apologizing for is unclear. But two thoughts come to mind. First, whatever has happened in his life probably served as a catalyst for his solo voyage. Second, even when faced with desperate circumstances that demand unvarnished candor, the sailor still can't quite say what he really feels.

"Even in his last note," Chandor said, "he was unable to communicate — he was blocked."