Underwater cameras were not used. The Williamson brothers had developed a system of watertight tubes and mirrors, like an upside-down periscope, and were dependent on the clarity of water and sunshine to provide the necessary light.
The actual undersea footage was shot in the Bahamas due to the unusually clear water. When this film was remade by Walt Disney 38 years later, they came to this same spot for their undersea footage.
The first motion picture filmed underwater.
This film became famous for its groundbreaking work in actual underwater photography by George M. Williamson and J. Ernest Williamson.