This 1957 classic stars John Carradine and Phyllis Coates and was produced and directed by Jerry Warren, who is clearly from the Ed Wood school of movie making. It opens with a lot of stock footage of waves, then stock shots of an octopus.
Then comes The Voiceover. "The sea. The birthplace of life. The great storehouse of minerals. The prison of haunting mysteries. The ocean is a dangerous jungle."
Sometimes these old movies have some great stock footage, and this film is no exception as off the top we see a real underwater battle between a shark and an octopus. (The shark wins.)
But can the film actually live up to this great opening? No, of course not. Don't be ridiculous. We actually get seven minutes into the film before the stock footage ends and the film proper actually starts, and this is only a 67 minute film.
Carradine plays Professor Wyman, who's invented a deep-sea diving bell. Unfortunately the cable snaps and the bell and the crew of two men and two women appears to have been lost. Coates, tv's original Lois Lane, plays a reporter on board the ill-fated diving bell. She apparently appeared in the film as a favour to the director who was an old friend, on the condition that the film would never be released in California. Much to her chagrin, the film did open in California and even worse, she never got paid for appearing in it.
The four survivors manage to escape the bell in wet suits but discover that it landed in an underground cave system full of air. They begin walking, hoping to find a way out of the immense cavern. They pass by a stock footage lizard, then they meet an old man wandering around the caves (who looks just like Michael Palin as the "It's..." man from Monty Python). The old man tells them that there's no way out. When faced with this terrible news, two of our survivors suddenly express they're long-secret love for each other. Naturally.
Professor Wyman builds another diving bell and saves the two male survivors. Meanwhile, the old man who looks like Michael Palin decides that he needs to keep one of the women for himself and attacks her. Fortunately, a nearby volcano happens to erupt and he is killed. The women flee the volcano and fortunately stumble upon the men and the new diving bell. They are rescued. Everyone lives. Huzzah.
This film is another case of false advertising in movie titles. Yes, it does take place in the World, but there is nothing Incredible about it and certainly nothing is Petrified.
Except maybe the acting.
But at least the actors got paid. Except for Coates, apparently.