The movie, to be released in December 2014, is based on Laura Hillenbrand's book "Unbroken: A World War II Story of Survival, Resilience, and Redemption," which chronicles Zamperini's life.
The former Olympian spent a harrowing 47 days afloat in the Pacific Ocean following the 1943 crash of his U.S. military plane. He spent the following two years as a prisoner of war after washing up behind Japanese enemy lines.
"Unbroken" will star Jack O'Connell as Zamperini. The screenplay is being fine-tuned by Joel and Ethan Coen.