In the laboratory, above the filing cabinets on the right was a aerial picture of the K-25 Plant, it was the largest building in the Manhattan Project and was authorized in late 1942, it was 11 miles from the WWII Secret City of Oak Ridge, Tenn. The plant was intended to produce enriched uranium. The photo on the left looks like it is a close up of K-25 but that has not been proven at this time.
The majority of the underwater scenes were shot at Catalina Island off the coast of Los Angeles. The close-ups were later filmed in a tank filled with water and plastic sea-weed.
The Salton Sea was formed from a Pre-dam flood of the Colorado River. The dam project that created Hoover Dam (boulder Dam) was a result of flood control. A boomtown grew around the lake, with all the typical real estate promotional hype. As the lake shrunk, and values dropped, the area became a near ghost town.