The PT boats seen at the beginning (and for a brief moment, at the end) of the film are Elco 77-foot PTs, the type of boat that saw intense combat against the Japanese Navy's "Tokyo Express" in the Guadalcanal area early in World War II. The wartime second-series Elco 77-footers, which were the same type as PT 59, John F. Kennedy's second command after PT 109 was rammed and sunk, are seldom seen on film, and hardly ever in color.
'The Hollywood Reporter' reported that the United States Navy would be having a recruitment station in the lobby of Grauman's Chinese Theatre for the Hollywood Premiere of this picture on 27 May 1942, planning to have it open for the whole of the movie's season at the theater.
During normal, unhurried dives, a submarine floods the ballast tanks. The dive planes are set for minimum down angle and the sub then slowly submerges. A crash dive is used when the sub must dive quickly to escape danger. In this case the tanks are flooded, the dive planes are set for extreme down angle and propellers are used to actually drive the sub under. The difference in the angle of descent between the two can be as much as 20-25 degrees.
Final film for Tyrone Power prior to entering military service as a private. He is credited in the film as as Tyrone Power U.S.M.C.R. On 1 October 1942, Power was allowed to defer the start of his military duties in order to complete production on this movie which did not finish shooting until mid-November 1942. Power did not star in another movie until 1946 when he appeared in The Razor's Edge (1946). At the time of Power's death in 1958, he was a Major in the United States Marine Corps Reserves.
This movie represents one of a select group of a few World War II submarine movies which 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. These movies include Crash Dive (1943); The Enemy Below (1957); Torpedo Run (1958) and U-571 (2000). The non-WW II sub-movie, 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.
Neither the later pictures Crash Dive (1996) nor its sequel Counter Measures (1998) (aka Crash Dive 2) are remakes of this film. They merely all share being submarine movies and being part of the sub-movie genre with a submarine term title.
According to the 'Hollywood Reporter', William Perlberg was originally going to be a producer on this picture. Milton Sperling was then assigned producing duties, but on 10 September 1942 he joined the Marine Corps. He was replaced by Lee S. Marcus, who joined the movie while it was in production.
The term "the smoking lamp is lit" is used several times. In the days before matches were widely available square rigger sailing ships provided a burning lamp so that smokers could light their pipes or cigars. It was usually located in the forecastle or near the galley where smoking was permitted. The term "the smoking lamp is lit" meant that smoking was permitted. The term "the smoking lamp is out" meant that smoking was not permitted due to dangerous proceedings such as handling gunpowder.