Top 10 Most Incredible Animal Journeys 2

Freshwater eels are born prepared for the rough waters they face in life. After hatching in the salty Sargasso Sea, the eels swim to freshwater rivers in the United Kingdom and the East Coast of North America. On the way, their kidneys adapt to the change in salinity. When it's time to lay eggs, the eels and their kidneys will return to their beginnings.