The Snorkel is a 1958 British thriller film directed by Guy Green and stars Peter van Eyck, Betta St. John and Mandy Miller.

Decker decides that he will have to kill Candy, and, establishing an alibi as before, lures her to the villa by telling her that he has found his wife's suicide note and has asked the police Inspector to come over as well.

He 'reads' Madge's suicide note to Candy and encourages her to drink a drugged glass of milk; by the time she realises that he has made up the story she is too drowsy and Decker continues to carry out his plan, hiding under the floorboards and the rug as before.

The film was the first starring vehicle for actress Mandy Miller; Green described her as "...a natural talent and a very professional girl, but a bit too mature for the part, and all our efforts failed to disguise this."

"[6] In The New York Times, critic Richard W. Nason wrote: "Hammer Films apparently has become proficient in the manufacture of motion pictures that are not greatly distinguished but that nonetheless manage to be more absorbing than the usual low-budget program film ... because of the competence of the direction, acting and particularly the editing, the audience is kept awake throughout the running of the twin bill.

"[9] Glenn Erickson of DVDTalk called van Eyck's character "underdeveloped but menacing," and noted that, "Mandy Miller's likeable teen heroine is a doubtful mix of immature emotions and steely resolve, as shown in one poorly handled scene when Candy underreacts to the death of her beloved dog."

However, he goes on to write, "The film's good reputation comes from fans that admire the killer's technically elaborate murder scheme, and ace Hammer cameraman Jack Asher's arresting camerawork.

A final surprise lifted from The Third Man [1949] could have provided a perfect shock finish, but the movie goes on a bit longer, clearly to tie up some moral loose ends for the censors.

"[3] John M. Miller, wrote for Turner Classic Movies: "The Snorkel opens with one of the more memorable pre-credits sequences to be found in a thriller ...