Johannes Schmidt spent 25 years chasing an enigmatic fish across the Atlantic Ocean. The Danish biologist surrendered the hunt only after his ship was torn to pieces on a Caribbean coral reef. Schmidt was trying to solve an ancient mystery about one of nature’s strangest fish: eels. Aristotle suggested the slithering species emerged spontaneously from the earth. But by the early 1900s, Schmidt and others suspected eels bred in the open ocean, instead of their lifelong freshwater homes.