They are hundreds of kilometers from the nearest ocean, yet in this footage first aired in the summer of 2012, you can spot dolphins—pink river dolphins—swimming through the Amazon. “Catching fish in the flooded forest would seem nearly impossible, but like bats, they use sonar to navigate and find their prey.” This National Dolphin Day, continue to dive through our Earth Month in the Amazon. | National Geographic Society

Pink Amazon dolphins stayed behind in rivers when sea levels dropped millions of years ago. See how their bodies adapted to survive. | National Geographic