Captain Ahab's mortal enemy is getting new life for "In the Heart of the Sea," and ET was behind the scenes for the making of the film.

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Ron Howard's action-adventure movie follows the aftermath of the real-life maritime disaster that inspired Herman Melville's "Moby Dick." In the winter of 1820, the New England whaling ship Essex was attacked by a whale, leaving the surviving crew to do the unthinkable to stay alive in the face of storms, starvation, panic and despair.

Chris Hemsworth stars as the vessel's veteran first mate Owen Chase, and he had to drop a good amount of weight to shoot the shipwrecked scenes. The action star goes from "Sexiest Man Alive" to one of the skinniest through a strict, meager diet.

"We have to shoot the really skinny stuff where we drop down to 5, 6, 700 calories a day, a good three or four weeks and it's going to be pretty uncomfortable, but we'll be together in our misery," Hemsworth told ET. "I spend more time thinking about food than anything else at the moment."

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"In the Heart of the Sea" hits theaters Dec. 11.