Trivia: After Ernest Hemingway guided two extremely expensive (and failed) offshore excursions for original marlin-fishing footage, Warner Brothers settled for existing footage of a world-record marlin caught off the coast of Peru by Alfred C. Glassell, Jr. His taut, heavy-duty fishing line can be seen bouncing wildly, high in the air, in the scene where the marlin finally breaches (even though the Old Man's hand-line is pretty much stationary and angled low to the ocean surface).
Trivia: During the film's formidable two years in production, actor Spencer Tracy lapsed back into alcoholism and found a ready drinking partner in author Ernest Hemingway. One night, while on one of their binges, the two even demolished a bar in Havana, Cuba, and the bar owner demanded that Warner Brothers Studios pay $150,000 in damages. Warner Brothers was so infuriated with Spencer Tracy that they were on the verge of firing him and replacing him with Ernest Borgnine. (source: "Spencer Tracy: Tragic Idol" by Bill Davidson).
Trivia: Spencer Tracy's hair was not naturally white when they first started filming "The Old Man and the Sea"; so, his hair was cosmetically bleached white for the part of Santiago. However, after a grueling two years in production and his lapse back into alcoholism, Tracy's hair naturally turned white by the time they finished the film.
Trivia: For close-ups of the giant marlin swimming near the skiff, Warner Brothers committed to building a giant, realistic, mechanical marlin with moving fins and tail, which was going to be deployed in actual open-ocean shots. Unfortunately, the first time it was lowered into Gulf Stream waters off the coast of Cuba, the elaborate mechanical marlin immediately sank and was never seen again. Thereafter, they used the much-less-realistic static marlin model that bobbed on the surface like a cork in a sound stage water tank (arguably the weakest scenes in the film).