“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 opening paragraphs of the book discuss a mysterious object in the water that many seafarers had been encountering in their travels. Until 1876, not much information was known about it. Those who saw it, however, agreed that it was huge and traveled through the water quickly. The strange object gripped the public imagination around the world and was considered an imminent danger to sea travelers.

“Three seconds after reading the letter of the honourable Secretary of marine, I felt that my true vocation, the sole end of my life, was to chase this disturbing monster, and purge it from the world.”

Professor Aronnax, the narrator of the story, receives a letter from the United States Government. Signed by the Secretary of Marine, it asks him to join an expedition on the Abraham Lincoln in pursuit of the mysterious object in the water—which everyone, including Professor Aronnax, has determined to be a monster. While Professor Aronnax had given no thought to such an endeavor before he receives the letter, he decides—a few seconds after reading it—that it is now his sole purpose in life. He feels it is his calling to pursue the monster and rid the world of such a menacing threat.

“The entire ship’s crew was undergoing a nervous excitement, of which I can give no idea: they could not eat, they could not sleep—twenty times a day, a misconception or an optical illusion of some sailor seated on the taffrail, would cause dreadful perspirations, and those emotions, twenty times repeated, kept us in a state of excitement so violent that a reaction was unavoidable.”

Once onboard the Abraham Lincoln, the whole crew is invested in finding the monster. Men of all ranks watch day and night, which keeps the mood tense. Although they often end up chasing a whale, everyone is constantly on edge with the prospect of finding the creature.