The only film Frank Miller directed alone.
The underwater scenes were all shot dry-for-wet, which greatly relieved Eva Mendes, who didn't know how to swim.
According to myth, Lorelei (death) was a siren who lured ships and sailors to destruction.
The names of Logos, Pathos, and Ethos for three of the characters in the film are from Aristotle, who suggested that these three elements are necessary for persuasive rhetoric.
Ebony White, the Spirit's sidekick from the comics, was omitted, largely because he was typically portrayed as a 1930's racial stereotype. Writer and director Frank Miller disliked the idea of the Spirit having a sidekick, so the character was completely removed, rather than updated.