: The film is based on Marshall Pugh’s 1956 book, Commander Crabb . It was produced just two years after the real Lionel Crabb vanished under mysterious circumstances during a Cold War reconnaissance mission for MI6 in 1956.
: Unusually for war films of the era, it avoids heavy jingoism, portraying the Italian divers not as fanatics but as skilled, professional adversaries performing dangerous work. The Silent Enemy(1958)
: It explores the psychological tension of an invisible enemy that attacks from the shadows of the harbor. : The film is based on Marshall Pugh’s