To simulate the U.S.S. Oklahoma capsizing, the crew constructed the world's largest-ever gimbal. It took special effects supervisor John Frazier four months to design, and four more months for he and production designer Nigel Phelps to build. It was made of pure steel and weighed 700,000 pounds. It could rise 25 degrees into the air, and do a 180 degree barrel turn. In the film, as the Oklahoma rolls over, the back 450 feet is CGI, but the front portion is the real gimbal, with over 150 real stuntmen on it.