The Brazilian Navy spotted something unusual in the azure waters of the South Atlantic. In 2015, at a remote outpost and biological research station on the island of Trindade, 1,100 kilometers off central Brazil, sailors spotted a small gray seal swimming in the waves. Two days later, they found its body on the island’s Catelha beach. Scientists who went to take a closer look made an astonishing discovery—the corpse was a young Weddell seal.