You wouldn’t think that Robert Redford would be able to play a survivalist this late in his life. At 77, the Hollywood sex symbol is, well, getting up there, and I thought for sure his Butch Cassidy and Jeremiah Johnson days were behind him.

And, yet, in J.C. Chandor’s “All is Lost” — in which Redford plays a nameless man who gets stranded on a sailboat in the middle of the ocean — he proves that he’s still got what it takes to fight and survive.

After we hear a voice-over monologue and see what appears to be a wrecked boat, “Our Man” (as Redford’s character is listed in the credits) is awakened by the sound of a stray shipping container crashing into the side of the boat. He doesn’t panic and springs immediately into action. You can tell he’s a seasoned sailor: His resourcefulness is pretty much instinct.

Redford still gives him an everyman quality: Nothing he does in “All Is Lost” feels exaggerated or unrealistic. He’s not like Bruce Willis in latest installment of “Die Hard,” who blindly jumps out a window and just happens to land on a nearby ledge. In other words, he isn’t a superhero.

For the movie’s entire hour-and-47-minute running time, it’s just Redford vs. the elements — we see no one else but him. Chandor makes “All is Lost” without any story fat to complicate things. We don’t see where Our Man comes from and how he got to be on the boat. There aren’t any flashbacks. The action doesn’t shift to another character or group of characters and, best of all, there aren’t any other one-dimensional meatheads on the boat with Redford to be killed. Considering that most survivalist movies do have these elements, this barebones method proves to be surprisingly effective and refreshing.

Since it is a one-man survival tale, Redford has about eight lines of dialogue total, and most of them are in that opening monologue. This means that the performance is mainly physical, which even for a young actor is difficult to pull off. This is where Redford’s old age actually comes in handy.

As intelligent and resourceful as the character is, you can also see that he’s a little frail. Sometimes he stumbles around the boat or struggles to do certain tasks, like pump water out of the boat. It gives his performance more dimensions; he’s not some strapping muscular lad who has perfect agility.

Redford also does a lot of great facial acting: His expressions of frustration, of fatigue and, most importantly, determination look 100-percent authentic. No matter how many times he gets knocked down (and sometimes he is literally knocked down or thrown off the boat by a wave), he never gives up.

Because Chandor’s style is so straightforward and naturalistic, it doesn’t feel sappy and sentimental. There are a few lingering poetic shots from underwater, showing a school of fish swim around the boat, but overall, “All is Lost” looks like a realistic depiction of someone stranded at sea.

Alex Ebert’s score can be heard faintly, but for the most part, Chandor lets the natural sounds within the movie’s environment speak for themselves: the roaring of the waves, the creaking of the boat, the splitting of the wood, the flapping of the sails in the wind and, sometimes, just silence.

Chandor is a rising writer/director to look out for. He’s only made two features (this one and the superb “Margin Call” in 2011), and he’s not only proven he can make high-quality pictures, but he’s also capable of working in different genres and styles. “Margin Call” was a Mamet-esque horror story about the early hours of the 2008 financial crisis. To go from that — an ensemble film and virtually all dialogue — to a virtually dialogue free, one-man survivalist story already shows impressive range.

“All is Lost” won’t be for everyone: It’s simple, non-spectacle style won’t be exciting enough for some, and other people will probably want that story fat I mentioned earlier.

There’s no explicit character development because it’s suggested in Redford’s actions and behaviors. And a lot of it is thanks to Redford — with a lesser actor “All is Lost” wouldn’t have been nearly as great.

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