17. Why do dolphins leap out of the water?

DOLPHINS AND WHALES HAVE TAILS THAT ARE FLATTNED HORIZONTALLY, not vertically like fish-tails. They swim by sweeping their tails up and down. When swimming at speed, dolphins leap out of the water to save energy, because it is quicker and easier to move through air than water. Like all water-dwelling mammals, dolphins must also surface to breathe.