Twenty Thousand Leagues Under the Sea as an inhabitant of British Colonial India, "is an inhabitant of an oppressed country". 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 breathing apparatus used by "Nautilus" divers is depicted as an untethered version
Twenty Thousand Leagues Under the Sea not to a "depth", as 20,000 leagues (80,000 km) is nearly twice the circumference of the Earth. The greatest depth mentioned in the book is four leagues. The book uses metric leagues, which are four kilometres each. During the year 1866, ships of several nations spot a mysterious sea monster, which some suggest to be a giant narwhal. The United States government assembles an expedition in New York City to find and destroy the monster. Professor Pierre Aronnax, a French marine biologist and narrator of the story, who happens to be in New York at the time, receives a last-minute