A mission to rid the seas of a monstrous creature becomes a terrifying nightmare when Professor Arronax, Conseil and Ned Land are thrown overboard. The huge marine animal which has haunted the water is no living beast, but a spectacular man-made vessel, and the three men find themselves the helpless prisoners of Captain Nemo. Resigned to their fate, they begin a miraculous journey on the submarine ship which can travel through waters never before explored. For the Professor, at least, this voyage is one he would not have missed for the world.
The year 1866 was signalised by a remarkable incident, a mysterious and puzzling phenomenon, which doubtless no one has yet forgotten. Not to mention rumours which agitated the maritime population and excited the public mind, even in the interior of continents, seafaring men were particularly excited. Merchants, common sailors, captains of vessels, skippers, both of Europe and America, naval officers of all countries, and the Governments of several States on the two continents, were deeply interested in the matter. For some time past vessels had been met by "an enormous thing," a long object, spindle–shaped, occasionally phosphorescent, and infinitely larger and more rapid in its movements than a whale. The facts relating to this apparition (entered in various log–books) agreed in most respects as to the shape of the object or creature in question, the untiring rapidity of its movements, its surprising power of locomotion, and the peculiar life with which it seemed endowed. If it was a whale, it surpassed in size all those hitherto classified in science. Taking into consideration the mean of observations made at divers times—rejecting the timid estimate of those who assigned to this object a length of two hundred feet, equally with the exaggerated opinions which set it down as a mile in width and three in length—we might fairly conclude that this mysterious being surpassed greatly all dimensions admitted by the learned ones of the day, if it existed at all. And that it DID exist was an undeniable fact; and, with that tendency which disposes the human mind in favour of the marvellous, we can understand the excitement produced in the entire world by this supernatural apparition. As to classing it in the list of fables, the idea was out of the question.