The longest-surviving shipwreck castaways were abandoned on a barren Indian Ocean island. With no wood to spark a new flame, they kept a single fire burning for an astonishing 15 years. In 1761, a French East India Company ship called L'Utile struck a reef. The crew managed to build a makeshift boat from the wreckage and sailed away, leaving behind 60 Malagasy people who had been illegally purchased as slaves in Madagascar. The sailors promised to return, but they never did. The castaways were marooned on a barely habitable sandbank—a flat, treeless coral atoll measuring less than a square kilometer. To survive, the marooned people had to rely entirely on what the tiny island could provide. They built robust shelters out of coral blocks and copper from the wreckage to withstand frequent cyclones. With no natural vegetation other than sparse scrub, they subsisted for a decade and a half on a diet of seabirds, turtles, and brackish water drawn from a hand-dug well. The single fire that sustained them had been originally lit from the shipwreck's embers and carefully guarded around the clock. Fifteen years later, in 1776, a French corvette commanded by Chevalier de Tromelin finally arrived. By then, only eight survivors remained: seven women and an eight-month-old baby boy. While the Tromelin castaways hold the record for the longest-surviving group, the longest documented solitary shipwreck survivor is Pedro Serrano. In 1526, Serrano swam to a barren Caribbean sandbank—now known as Serrana Bank—after his ship sank. He lived there for eight years, surviving by drinking turtle blood and rainwater before he was finally rescued in 1534. Like the Tromelin survivors, Serrano owed his life to the harsh but sustaining ecosystem of an isolated reef.