In an interview in July 1977 with 'The New York Times', Curd Jürgens00who played the German submarine commander Capt. Von Stolberg--"This was an important picture for me because it was the first film after the war in which a German officer was not interpreted as a freak."
Two endings were shot: In one, both commanders die; in the other, a third vessel rescues them. The final ending was determined by preview results. The "USS Haynes" was in actuality the USS Whitehurst, captained by Walter R. Smith, who received a "technical advisor" credit and can be seen playing the ship's chief engineer. Eva Novak can be seen in a photo as the wife of Von Stolberg.
The destroyer escort "USS Haynes" was in real life the USS Whitehurst (DE-634). The cast spent about a month filming on board this vessel. Many of the crew appeared in this movie. 20th Century-Fox production notes from the AMPAS Library declare that the USS Whitehurst was a battle-hardened veteran from the Second World War which had been berthed at Pearl Harbor, Hawaii.
The tune sung by the U-Boat crew between the one-per-hour depth charge attacks, after the scene with the panicking torpedo man and the wrench, is from an 18th-century march called "Der Dessauer Marsch". A popular song, it's also known by the first line of lyrics: "So leben wir" (translation: "That's how we live").
According to Robert Osborne, Robert Mitchum fell down one of the ship's gangways while shooting, and was severely injured, requiring him to wear a back brace for the duration of filming. Also, some depth charges fired from the Navy destroyer used in the film were accidentally launched at the same time, causing damage to the ship's rudder and its hull.
This movie represents one of a select group of World War II submarine movies that have won the one single Academy Award in a technical category, that's just only the one Oscar in either special effects or sound editing. The others are Crash Dive (1943); The Enemy Below (1957); Torpedo Run (1958) and U-571 (2000). The Hunt for Red October (1990) also won just the one Oscar as did the WW 2 part sub-movie 49th Parallel (1941), but for Best Original Story.
Lt. Cmdr. Walter R. Smith (I)' was captain of the USS Whitehurst, which stood in for the "USS Haynes". Publicity material from 20th Century-Fox states that Smith was a technical advisor to the production and also played the ship's Chief Engineer. However, he is not credited as such in the films credits, which state that Robert Boon played the Chief Engineer. Smith may be the character who can be seen in the movie reading the comic "Little Orphan Annie".
The U-Boat seen in this movie is far roomier and more spacious, cleaner and tidier than the real German U-boats of World War II (which were more realistically depicted in the later movie Das Boot (1981)). During the Second World War, these subs did not have passageways and private rooms and were dirty and cramped. Since the U-boat's "head" (toilet) could not be used at depth, the crew was forced to use buckets which, during depth charge attacks, frequently spilled. It was said that when a U-boat returned to base the smell inside the boat was enough to make dockworkers who went aboard vomit.
Some of D.A. Rayner's wartime submarine adventures and experiences that appeared in his novel "The Enemy Below", on which this film is based. Rayner wrote another naval warfare book "Escort: the Battle of the Atlantic", about an encounter between German U-boat U-2000 and Allied corvettes on Nov. 11, 1944, off the coast of southern Ireland.
The finale rescue was shot on location in the sea off of Long Beach, CA, and on the USS Alfred E. Cunningham (DD-752), an Allen M. Sumner-class destroyer. Other location filming sites included the Pacific Ocean near Oahu, HI, for scenes on the USS Whitehurst, as the USS Haynes.
The captain of the destroyer escort (DE) tells a sailor (radio operator) to maintain radio silence to keep the submarine from concluding it is being followed by a ship. But the DE would have already alerted the sub of its presence by the DE's radar transmitter signal.
In an ironic twist, the engineering officer, played by the ship's real-life commander Walter R. Smith, is seen reading a "Little Orphan Annie" comic while, in the same scene, an enlisted sailor is reading Edward Gibbon's classic "The Decline and Fall of the Roman Empire."
Darryl F. Zanuck: (at around 62 mins) The Captain calls a conference of all officers and chiefs in the wardroom. At the left rear of the wardroom there is a chief in blue clothing with a blue May West life preserver--it is Zanuck, who at the time was the head of 20th Century-Fox Pictures.
Eva Novak: As the wife of German submarine commander Von Stolberg (Curd Jürgens). Though Novak neither appears in the live-action of the movie itself nor is listed in the cast credits, she is seen in a photograph appearing as Mrs Stolberg.
The trivia items below may give away important plot points.
According to the Australian DVD sleeve notes, "Producer-Director Dick Powell let the public decide the ending for The Enemy Below (1957). He filmed the movie with two endings, then let a preview audience vote for the ending they liked best. The ending he used won by unanimous vote." The ending which wasn't used had both submarine commanders, Captain Murrell (Robert Mitchum) and Von Stolberg (Curd Jürgens) die by drowning at the end of this picture when Murrell dives into the sea to rescue Von Stolberg. The used ending was the happy ending which had both of them rescued by a ship. Details of the two endings were reported in a July 1957 edition of 'The Hollywood Reporter' which stated that Powell filmed the two endings because he thought that the original ending (the unused one) was too bleak.
Though "The Enemy Below" is a story about a single destroyer against a U-Boat, in the history of World War Two naval warfare there was never a battle between a single destroyer against a submarine for a long period of time.