The character Perry Lawton brought back 600 carats (just over 1/4 pound) of diamonds from the underwater city. Even if all the diamonds were industrial grade, this was a great fortune.
Although this was only special effects director Eiji Tsuburaya's next-to-last film, it was also not only his last sci-fi/fantasy film, but the last time he would work with director IshirĂ´ Honda, with whom he worked on many of Toho's classic tokusatsu movies, including the Godzilla series.
His screenplay, based on his original stories, would be the last work in the film industry for Ted Sherdeman, ending a career in motion pictures that lasted about 20 years.
Lucretia, the evil Malic's companion, was played by 'Patricia Medina'. At the time this was filmed, she was married to Joseph Cotten who was playing good guy Captain Craig McKenzie.
The trivia items below may give away important plot points.
Upon arriving at Latitude Zero, Lawton asks Captain MacKenzie if taking photographs is permitted to which MacKenzie replies "Not at all, Mr. Lawton". Lawton then, seemingly hearing what he wants to hear, says "Good, 'cause no one's gonna believe me unless I show them pictures" and for the rest of the film, proceeds to snap everything he can. At the end, after being permitted to return to the surface, it is revealed that his rolls of film are all blank.