A strange giant "sea monster" has been rampaging the seas. The United States naval ship Abraham Lincoln is sent to investigate, but the vessel is rammed and damaged by the "monster" which turns out to be Nautilus, the technologically advanced submarine of the enigmatic Captain Nemo. The Abraham Lincoln, now rudderless from the attack, is adrift. Then, in a "strange rescue", Nemo guides his submarine directly beneath four people who had been aboard the American ship and who had fallen into the sea during the attack. Nautilus surfaces and Nemo's own crew now bring the four individuals into the submarine through one of its deck hatches. The four include the master harpooner Ned Land, the French professor Pierre Aronnax, his daughter, and the professor's assistant. Once aboard the submarine, the four are required by Nemo to pledge they will not attempt to escape. The captain then introduces them to his vessel and to the wonders of its underwater realm. He later takes them hunting on the sea floor. Meanwhile, not far from the submarine, soldiers in a runaway Union Army balloon are marooned on a mysterious island, where they find a wild girl living alone. Soon the yacht of Charles Denver arrives at the island. A former British colonial officer in India, he has been haunted by the ghost of a woman whom he attacked years ago. Rather than submit to him sexually, she had stabbed and killed herself. Denver then fled with her young daughter but later abandoned the child on the island. Long tormented by what he had done, he has returned to find the girl or to determine what happened to her. One of the Union soldiers schemes and kidnaps the wild girl onto Denver's yacht. Another soldier swims aboard to rescue her. At the same time, Nemo discovers that the yacht belongs to Denver, the enemy he has been seeking all these years. The Nautilus destroys the yacht with a torpedo, but the girl and her rescuer are saved from the water by Captain Nemo. In elaborate flashback scenes to India, Nemo reveals that he is Prince Daaker, and that he created the Nautilus to seek revenge on Charles Denver. He is overjoyed to discover that the abandoned wild girl is his long-lost daughter, but his emotion is such that he expires. His loyal crew bury him at the ocean bottom. They disband and the Nautilus is left to drift.
This was the first motion picture filmed underwater. The underwater scenes were photographed by the Williamson Submarine Film Corporation in the Bahamas. Actual underwater cameras were not used, but a system of watertight tubes and mirrors allowed the camera to shoot reflected images of underwater scenes staged in shallow sunlit waters. The film was made by The Universal Film Manufacturing Company, not then known as a major motion picture studio. Yet in 1916, they financed this film's innovative special effects, location photography, large sets, exotic costumes, sailing ships, and full-size navigable mock-up of the surfaced submarine Nautilus. The film took two years to make, at a cost of $500,000. Hal Erickson has said that "the cost of this film was so astronomical that it could not possibly post a profit, putting the kibosh on any subsequent Verne adaptations for the next 12 years".
