to Bessie. He helps the Navy locate Nazi U-boats by signaling with his "thrum", and plays a large part in the Allied victory in the Battle of the Atlantic. In his final mission, he is nearly killed when the Nazis develop a "thrum"-seeking torpedo and is further handicapped by the loss of his spectacles. He manages to survive using Crusty as his "navigator", and sinks U-boats by redirecting their torpedoes. After the battle, he swims to Coney Island to say goodbye to Bessie, who gives him a replacement set of glasses. He then swims off with Ladyfish. In the film's coda, back in 1963, George and the Admiral travel out to sea to contact Limpet about whether he is training the porpoises. Cast Don Knotts as Henry Limpet Carole Cook as Bessie Limpet Jack Weston as Machinist's Mate 2nd Class (PO2) George Stickle Andrew Duggan as Harlock Larry Keating as Admiral P.P. Spewter Oscar Beregi, Jr. as Nazi admiral Charles Meredith as Fleet Admiral Elizabeth MacRae as Ladyfish (voice) Paul Frees as Crusty (voice) Phil Arnold as Short Fishman (uncredited) This was the last film of Larry Keating and Charles Meredith; both died not long after it was finished. Production The film was based on a novel by Theodore Pratt which was published in 1942. Jon Rose and Jonathan Brewer wrote the script, with Rose producing through Warners. Don Knotts signed in March 1962. He planned on making the film on hiatus from The Andy Griffith Show. It was his first lead role in a film. Lubin signed to make the film in July, and filming took place on the Warner backlot later that same month. Both Don Knotts and Elizabeth MacRae (Limpet and Ladyfish) were employed in Andy Griffith's Mayberry franchises, respectively as deputy Barney Fife and Lou-Ann Poovie, Gomer Pyle's girlfriend in the later seasons of Gomer Pyle, U.S.M.C.. During World War I and World War II, there was a mine known as a limpet, a type of naval mine attached to a target by magnets named because of their superficial similarity to the limpet, a type of mollusk. "Das Limpet" was the German Navy's identification of Don Knott's character. The destroyer was the naval ship featured in this film. Another ship used in filming was the cruiser , which was referred to as in the film. The cruiser was offered for use at the time of pre-production