Dark Waters (Once Upon a Time) is to take Snow's heart. The Land of Untold Stories is revealed to be the Mysterious Island from the book as the same name. The "Nautilus" is based on the submarine from "Twenty Thousand Leagues Under the Sea". Captain Nemo based on the protagonist from Jules Verne's novel "Twenty Thousand Leagues Under the Sea". Hook refers to the giant squid that attacks him as a kraken. The kraken is a legendary sea monster of giant size that is said to dwell off the coasts of Norway and Greenland. The episode posted its lowest numbers so far in the series, as
Twenty Thousand Leagues Under the Sea public-domain translation, which is available from a number of sources, notably a recent edition with the title "Twenty Thousand Leagues under the Seas" (). In 2010 Walter released a fully revised, newly researched translation with the title "20,000 Leagues Under the Seas" — part of an omnibus of five of his Verne translations titled "Amazing Journeys: Five Visionary Classics" and published by State University of New York Press. In 1998 William Butcher issued a new, annotated translation from the French original, published by Oxford University Press, , with the title "Twenty Thousand Leagues under the Seas". He includes detailed notes,