Dr. Halstead (Carl Benton Reid) of the Institute of Oceanography hires Bob Gage (William Lundigan) to supervise the construction of an underwater city.

If humans are going to blow themselves sky-high at some point in the future, then it might be a good idea to have an escape hatch down at the bottom of the ocean.

A series of underwater living units are carefully created and tested until it seems that they are ready for residents to move in.

[3] Alex Gordon recalls that his wife was inspired by an article in American Weekly magazine about scientists growing food on the ocean floor.

Gordon also recalled that the original choice for Dr. Halstead, Raymond Massey was replaced when he couldn't arrive in time to commence production.