The United States Destroyer used in the film was the USS Alfred A. Cunningham (DD-752) which was commissioned on Thursday, November 23rd, 1944. It served in World War II and the Korean War before being decommissioned in 1971. It was sunk as a target in 1979.
This was the final animated film work released by Warner Brothers before the animation studio was shut down. Warners would continue to release theatrical shorts produced by Depatie-Freleng Enterprises until 1969.
Prior to the film's release, Warner Bros. distributed a promotional short subject to theaters documenting a press junket to Weeki Wachee Springs, Florida where reporters watched a preview of the movie erroneously hailed as "the world's first underwater movie premiere." (The audience sat in a submerged auditorium and watched movie through a glass wall as it was projected on an underwater lagoon screen.) Actually, the same sort of stunt had been staged at least once before, when reporters donned swimming suits and oxygen tanks to view the 1955 Jane Russell movie Underwater! (produced by Howard Hughes) in another Florida lagoon.
A remake has been long in development. Don Knotts was aware of plans for the remake, which he wrote about in his autobiography. At the time, Jim Carrey was up for the role and Knotts offered his support. Director Kevin Lima was attached with Zach Galifianakis in the lead role, but both soon left the project. The attached director at the moment is Richard Linklater.
The ship launch shown at the start of the movie is stock footage of the SS Fred Morris going down the slipway on 2 November 1940 (in New Jesey, not Brooklyn); the ship was later acquired by the US Navy to become USS Otus and received one battle star for service in World War II.
Henry Limpet, after falling into the ocean and become a fish, done 37 thrums or shout of noise, as in fear or shock, that lead to Nazi's hitting themselves. There were 37 thrums, total. 10 to 15 thrums were heard twice or three times, but there were 37 thrums, done in the movie. And 2 more thrums were added in the movie's closing credits, totaling 39 thrums.
Although Bill Tytla was credited as the supervising animation director, a combination of health issues and disagreements with producer John C. Rose led to Robert McKimson taking over most of the animation directing duties early in production.