 The illusion of the Red Sea parting was achieved by large "dump  tanks" that were flooded, then the film was shown in reverse. The  two frothing walls of water were created by water dumped constantly  into "catch basin areas" then the foaming, churning water was  visually manipulated and used sideways for the walls of water. A  gelatin substance was added to the water in the tanks to give it  more of a sea water consistency. Although the dump tanks have long  since been removed, the catch basin section of this tank still  exists today on the Paramount lot, directly in front of the exterior  sky backdrop, in the central portion of the studio. It can still be  flooded for water scenes, but when not being used in a production,  it is an extension of a parking lot.