How do you PART A SEA before the era of CGI (and with the lack of divine assistance)? Cecil B. DeMille filmed two large "dump tanks" being flooded with water, then spun the film in reverse. The two frothing walls of water were created by water dumped constantly into "catch basin areas"; the churning water images were then flipped sideways to make the walls of water. A gelatin substance was also added to the water in the tanks to give it more of a seawater consistency.

Fun fact: A portion of the tank still exists today on the Paramount lot. It can still be flooded for water scenes, but when not being used in a production, it is an extension of a parking lot.