While visiting his friend Ray Harryhausen on the set, Ray Bradbury was given a copy of the script (which was going under the working title "Monster From the Sea") and was asked if he could possibly do some rewriting on it. After reading the script, Bradbury remarked about a scene in the story (which featured the monster destroying a lighthouse) that seemed very similar to a short story that he had published in "The Saturday Evening Post" several years earlier called "The Beast From 20,000 Fathoms". Bradbury's story was about a dinosaur that destroys a lighthouse. The next day Bradbury received a telegram offering to buy the film rights to the story. After the sale, the films title was changed to "The Beast From 20,000 Fathoms". Years later when Bradbury had his story reprinted he changed the title to "The Fog Horn".

http://www.nea.gov/av/video/bradbury/bradbury.html