In 1826 Captain Jules Dumont d’Urville, a French scientist and naval officer, was caught in a turbulent storm while crossing the Indian Ocean. He watched as a wall of water rose some 100 feet above his ship, the Astrolabe. It was one of several waves more than 80 feet tall that he recorded during the wild storm. One of his crew was lost to the sea. Yet after Dumont d’Urville made it back to land, his story, backed by three witnesses, seemed so outlandish that it was dismissed as fantasy.

Scientists at the time believed waves could only reach about 30 feet tall, so the handful of 19th century reports of massive waves rising in the open ocean were