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
20,000 Leagues Under the Sea: Submarine Voyage (as it was known to the employees) where the "helmsman" stood and controlled the vehicle's operation. The "diving" effect was produced by bubble machines located throughout the attraction, as well as using the waterfalls at the entrance to the show building. Each of the twelve vehicles accommodated a total of forty riders. Vehicles normally cycled through the attraction in packs of three. Despite the extensive 20,000 Leagues Under The Sea overhaul the attraction was given, essentially it was still the same as its Californian counterpart Submarine Voyage, in both its underwater show scenes and narration, except for a few occasional