French Professor Aronnax and his servant join the Abraham Lincoln, an American frigate, on a mission to find and destroy a "sea-unicorn of colossal dimensions, armed not with a halberd, but with a real spur, as the armored frigates." The undersea monster is thought to be responsible for the disappearance of over 200 ships. When they encounter the "gigantic cetacean" it disables the Abraham Lincoln and knocks Professor Aronnax, his servant, and the hot-tempered harpooner, Ned Land overboard. The three must cling to the beast or drown; soon they realize that it is really a man-made underwater vehicle.