He discovered these animals were a larval form of eels. He also found that the animals gradually drift to the edges of the Sargasso Sea where currents eventually catch and carry them close to where they'll spend most of their lives. In the spring, about 15 months or so after they're born, they have drifted near streams and estuaries along the continent. Glass eels can assume characteristics of either gender and split into two groups upon approaching freshwater. While some stay in tidal areas along the coast and become males, others move upstream into creeks, rivers and lakes and become females.
Yellow eels are what divers often see writhing about in Florida's freshwater springs.
Within a decade or so, and some speculate for a much longer period, yellow eels undergo still another remarkable change, which includes developing special cells for riding their bodies of excessive sea salts and forming enlarged eyes. This prepares them for the long swim to the Sargasso Sea. Their yellow-green covering changes into a metallic sheen, with their backs turning purplish black. No longer freshwater creatures of the night, they have now become marine fish. From late summer to November, most silver eels leave inland waterways.