In 1850, author Herman Melville visits innkeeper Thomas Nickerson, the last survivor of the whaleship Essex's last voyage, offering money in return for his story. Nickerson initially refuses, but finally agrees when his wife intervenes. The story turns to 1820: a whaling company has refitted the Essex to participate in the lucrative whale oil trade, and 14-year-old Nickerson signs on as a cabin boy. The owners hire veteran whaler Owen Chase as first mate, though he is disappointed not to receive a captain's commission. The captain is George Pollard, an inexperienced mariner from an established whaling family who envies Chase's skill and popularity. Chase and Pollard clash, leading Pollard to sail into a storm against Chase's advice, nearly sinking the ship. The two agree to put their differences aside rather than risking their reputations by returning to port without profit, and soon, the crew kills their first whale.
However, three months pass with no further successes, and Pollard realizes that the Atlantic is fished out. The Essex sails for the Pacific hoping for better luck. In Ecuador, the officers meet a Spanish captain who tells them his crew found the bountiful "Offshore Grounds" 2,000 miles to the west, but claims that a vengeful "white whale" destroyed his ship. Enthralled by the prospect, and disbelieving of the white whale story, Pollard and Chase lead the expedition west. They find the undisturbed grounds, but when they launch the whaling boats, the white whale, a massive bull sperm whale, attacks, damaging the boats and turning on the ship. Chase harpoons it from the Essex's deck, but the whale stoves the ship, killing two men. The crew abandons the Essex on the three intact whaling boats, and must sail hundreds of miles to shore on very limited supplies. The whale follows and attacks again, but they escape to the tiny Henderson Island. While gathering food, Chase discovers the corpses of earlier castaways, and concludes that the crew will die before another ship passes by. Four men decide to stay, while the rest set sail again on the boats. Soon after, one of the men dies, and the remaining crew reluctantly decide to cannibalize him.
The elderly Nickerson is overcome by emotion and stops his story. However, when his wife comforts him, he feels encouraged enough to finish. Back in the 1820s, the three boats separate and one is lost. The other two further resort to cannibalism to survive, with Pollard's cousin sacrificing himself. The whale returns, but Chase decides not to attack and it leaves forever. A passing ship rescues Pollard's boat, but Chase's boat continues to drift with no food or water. Finally, with the survivors on the verge of death, they reach land. The survivors return to Nantucket and their families. The ship's owners ask Pollard and Chase to cover up the story to protect the industry, but after Chase refuses to go along, Pollard reveals the truth in the inquiry. Nickerson relates that Chase continued sailing and became a merchant captain, while Pollard led another expedition to kill the whale, but the ship wrecked and he was forced to retire. Melville departs to compose his novel, Moby-Dick; the film ends as he writes the first line: "Call me Ishmael"
