According to the opening credits, Richard Attenborough appeared by arrangement with the Boulting Brothers.
Armstrong's quote, 'And all I ask is a tall ship/ And a star to steer her by" is from the poem, "Sea-Fever", by John Masefield.
Shortly after filming was completed in 1950, the submarine HMS Truculent went down in the River Thames with a heavy loss of life. The incident is referenced in the opening credits, and nearly caused the film to be withdrawn from distribution.
The opening credits state as a disclaimer: "This film does not portray the latest Admiralty developments in submarine escape and salvage." Similary, this message is reiterated during the film's closing credits by saying "this film . . . does not portray the latest developments in submarine escape and salvage."
This film's opening prologue states: "This film was completed before the tragic loss of H.M.S. Truculent, and earnest consideration has been given as to the desirability of presenting it so soon after this grievous disaster. The Producers have decided to offer the film in the spirit in which it was made as a tribute to the officers and men of H.M. Submarines, and to the Royal Navy of which they form a part."