The title refers to the distance traveled under the sea and not to a depth, as 20,000 leagues is over 15 times the radius of the earth. The greatest depth mentioned in the book is four leagues. A literal translation of the French title would end in the plural "seas", thus implying the "seven seas" through which the characters of the novel travel. However the early English translations of the title used "sea", meaning the ocean in general, as in "going to sea".
The word leagues in the English title is a literal translation of lieues, but refers to French leagues. The French league had been a variable unit but in the metric era was standardized as 4 km. Thus the title distance is equivalent to 80,000 km (twice around the Earth) or roundly 50,000 statute miles. In common English usage 1 league equals 3 statute miles.
As the story begins in 1866, a mysterious sea monster, theorized by some to be a giant narwhal, is sighted by ships of several nations; an ocean liner is also damaged by the creature. The United States government finally assembles an expedition in New York City to track down and destroy the menace. Professor Pierre Aronnax is a noted French marine biologist and narrator of the story; as he happens to be in New York at the time and is a recognized expert in his field, he is issued a last-minute invitation to join the expedition, and he accepts. Canadian master harpoonist Ned Land and Aronnax's faithful assistant Conseil are also brought on board.
Title page (1871)
The expedition sets sail from Brooklyn aboard a naval ship called the Abraham Lincoln, which travels down around the tip of South America and into the Pacific Ocean. After much fruitless searching, the monster is found, and the ship charges into battle. During the fight, the ship's steering is damaged, and the three protagonists are thrown overboard. They find themselves stranded on the "hide" of the creature, only to discover to their surprise that it is a large metal construct. They are quickly captured and brought inside the vessel, where they meet its enigmatic creator and commander, Captain Nemo (a name meaning "no one" in Latin).
The rest of the story follows the adventures of the protagonists aboard the submarine, the Nautilus, which was built in secrecy and now roams the seas free of any land-based government. (As further discussed below, the story was written decades before submarines of such size and utility became a reality.) Captain Nemo's motivation is implied to be both a scientific thirst for knowledge and a desire for revenge on (and self-imposed exile from) civilization. Captain Nemo explains that the submarine is electrically powered, and equipped to carry out cutting-edge marine biology research; he also tells his new passengers that while he appreciates having an expert such as Aronnax with whom to converse, they can never leave because he is afraid they will betray his existence to the world. Aronnax is enthralled by the undersea vistas he is seeing, but Land constantly plots to escape.
Nautilus's route through the Pacific
Nautilus's route through the Atlantic
Their travels take them to numerous points in the world's oceans, some of which were known to Jules Verne from real travelers' descriptions and guesses, while others are completely fictional. Thus, the travelers witness the real corals of the Red Sea, the wrecks of the battle of Vigo Bay, the Antarctic ice shelves, and the fictional submerged Atlantis. The travelers also don diving suits to go on undersea expeditions away from the ship, where they hunt sharks and other marine life with specially designed guns and have a funeral for a crew member who died when an accident occurred inside the Nautilus. When the Nautilus returns to the Atlantic Ocean, a "poulpe" (usually translated as a giant squid, although the French "poulpe" means "octopus" in French) attacks the vessel and devours a crew member. Shortly afterward, they are tracked and attacked by a mysterious ship. Nemo ignores Arronax's pleas for amnesty for the boat and attacks. Nemo attacks the ship under the waterline, sending it to the bottom of the ocean with all crew aboard as Arronax watches from the salon. Nemo bows before the pictures of his wife and children and is plunged into deep depression after this encounter, and "voluntarily or involuntarily" allows the submarine to wander into an encounter with the Moskstraumen, more commonly known as the "Maelstrom", a whirlpool off the coast of Norway. This gives the three prisoners an opportunity to escape; they make it back to land alive, but the fate of Captain Nemo and his crew is not revealed.
Captain Nemo's name is a subtle allusion to Homer's Odyssey, a Greek epic poem. In The Odyssey, Odysseus meets the monstrous cyclops Polyphemus during the course of his wanderings. Polyphemus asks Odysseus his name, and Odysseus replies that his name is "ουτις," which translates as "No-man" or "No-body". In the Latin translation of the Odyssey, this pseudonym is rendered as "nemo", which in Latin also translates as "No-man" or "No-body". Similarly to Nemo, Odysseus is forced to wander the seas in exile (though only for 10 years) and is tormented by the deaths of his ship's crew.
Commander Matthew Fontaine Maury, "Captain Maury" in Verne's book, a real-life oceanographer who explored the winds, seas, currents, and collected samples of the bottom of the seas and charted all of these things, is mentioned a few times in this work by Jules Verne. Jules Verne certainly would have known of Matthew Maury's international fame and perhaps Maury's French ancestry.
References are made to three other Frenchmen. Those are Jean-François de Galaup, comte de La Pérouse, a famous explorer who was lost while circumnavigating the globe; Dumont D'Urville, the explorer who found the remains of the ill-fated ship of the Count; and Ferdinand Lesseps, builder of the Suez Channel and the nephew of the man who was the sole survivor of De Galaup's expedition. Verne was an investor in Lesseps to build the French sea level crossing in Panama. The Nautilus seems to follow the footsteps of these men: She visits the waters where De Galaup was lost; she sails to Antarctic waters and becomes stranded there, just like D'Urville's ship, the Astrolabe; and she passes through an underwater tunnel from the Red Sea into the Mediterranean.
The crew of the Nautilus observes an underwater funeral.
The most famous part of the novel, the battle against the school of giant squid, begins when a crewman opens the hatch of the boat and gets caught by one of the monsters. As he is being pulled away by the tentacle that has grabbed him, he yells "Help!" in French. At the beginning of the next chapter, concerning the battle, Aronnax states that: "To convey such sights, one would take the pen of our most famous poet, Victor Hugo, author of The Toilers of the Sea". The Toilers of the Sea also contains an episode where a worker fights a giant octopus, wherein the octopus symbolizes the Industrial Revolution. It is probable that Verne borrowed the symbol, but used it to allude to the Revolutions of 1848 as well, in that the first man to stand against the "monster" and the first to be defeated by it is a Frenchman.
Some of Verne's ideas about the not-yet-existing submarines which were laid out in this book turned out to be prophetic, such as the high speed and secret conduct of today's nuclear attack submarines, and (with diesel submarines) the need to surface frequently for fresh air. However, Verne evidently had no idea of the problems of water pressure, depicting his submarine as capable of diving freely even into the deepest of ocean deeps, and with humans in diving suits able to emerge and walk along the deep ocean floor - where in reality, they would have been instantly crushed.
Model of the 1863 French Navy submarine Plongeur at the Musée de la Marine, Paris.
The Nautilus as imagined by Jules Verne.
Verne took the name "Nautilus" from one of the earliest successful submarines, built in 1800 by Robert Fulton, who later invented the first commercially successful steamboat. Fulton's submarine was named after the paper nautilus because it had a sail. Three years before writing his novel, Jules Verne also studied a model of the newly developed French Navy submarine Plongeur at the 1867 Exposition Universelle, which inspired him for his definition of the Nautilus. The world's first operational nuclear-powered submarine, the United States Navy's USS Nautilus (SSN-571) was named for Verne's fictional vessel.
Verne can also be credited with glimpsing the military possibilities of submarines, and specifically the danger which they possessed for the naval superiority of the British Navy, composed of surface warships. The fictional sinking of a ship by Nemo's Nautilus was to be enacted again and again in reality, in the same waters where Verne predicted it, by German U-boats in both World Wars.
The breathing apparatus used by Nautilus divers is depicted as an untethered version of underwater breathing apparatus designed by Benoit Rouquayrol and Auguste Denayrouze in 1865. They designed a diving set with a backpack spherical air tank that supplied air through the first known demand regulator. The diver still walked on the seabed and did not swim. This set was called an aérophore (Greek for "air-carrier"). Air pressure tanks made with the technology of the time could only hold 30 atmospheres, and the diver had to be surface supplied; the tank was for bailout. The durations of 6 to 8 hours on a tankful without external supply recorded for the Rouquayrol set in the book are greatly exaggerated.
No less significant, though more rarely commented on, is the very bold political vision (indeed, revolutionary for its time) represented by the character of Captain Nemo. As revealed in the later Verne book The Mysterious Island, Captain Nemo is an Indian, who took to the underwater life after the suppression of the 1857 Indian Mutiny, in which his close family members were killed by the British.
This change was made on request of Verne's publisher, Pierre-Jules Hetzel (who is known to be responsible for many serious changes in Verne's books), since in the original text the mysterious captain was a Polish nobleman, avenging his family who were killed by Russians. They had been murdered in retaliation for the captain's taking part in the Polish January Uprising (1863). As France was allied with Tsarist Russia, to avoid trouble the target for Nemo's wrath was changed to France's old enemy, the British Empire. It is no wonder that Professor Pierre Aronnax does not suspect Nemo's origins, as these were explained only later, in Verne's next book. What remained in the book from the initial concept is a portrait of Tadeusz Ko?ciuszko (a Polish national hero, leader of the uprising against Russia in 1794) with inscription in Latin: "Finis Poloniae!".
The national origin of Captain Nemo was changed during most movie realizations; in nearly all picture-based works following the book he was made into a European. Nemo was represented as an Indian by Omar Sharif in the 1973 European miniseries The Mysterious Island. Nemo is also depicted as Indian in a silent film version of the story released in 1916 and later in both the graphic novel and the movie The League of Extraordinary Gentlemen.