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The murder of "Madge" is shown before the onscreen credits roll. Although the murderer's name is "Jacques Duval" in the Variety review, he is called "Paul Decker" in the film. The Variety and Daily Variety reviews give the film's running time as 73 minutes, but the viewed print was 90 minutes. The Variety review states that the film was based on a novel by Anthony Dawson, but the SAB indicates that the film was based on a motion picture story by Dawson and the onscreen credits read "from The Snorkel by Anthony Dawson." Although Hollywood Reporter production charts note that the film was shot on location in Italy, the Variety review states that it was filmed on the French Riviera. The Snorkel was one of several Hammer productions that were part of a co-financing arrangement with Columbia.