Although it is supposed to be based on Rafael Sabatini's novel "The Black Swan", in fact the story is completely original, and the only character retained from the original novel is the historical personage Henry Morgan.
The original ending was scrapped and a new one shot so that the film would pass the censor. The original ending had both Tyrone Power's and Maureen O'Hara's character jumping into the sea.
The ship in the picture was also used in the films That Hamilton Woman, The Princess and the Pirate and Captain Kidd.
Three of the cast-members in "The Black Swan" won Supporting Actor Oscars at some point in their careers: Thomas Mitchell for Stagecoach, George Sanders for All About Eve, and Anthony Quinn for both Viva Zapata! and Lust for Life.
To help out the war effort, the actors tried hard to keep the number of takes low so as to conserve film. Roughly thirty of the scenes were done in one take.