Watch any whale in motion – such as a dolphin riding a boat’s bow wave – and you’ll notice that whales are superb swimmers.
Their streamlined teardrop shape minimises drag from the water. Flukes have a rounded leading edge that tapers at the rear – similar to a wing. So thrust is created by both upward and downward strokes of the flukes.
Whales’ forelimbs have become rigid flippers, providing great manoeuvrability. And just as a yacht has a keel to provide stability, most whales have a dorsal fin.
Managing movement in the water
Look at the bones of a dolphin flipper and the X-ray of a young humpback whale flipper. Compare them with the X-ray of a human hand.
You might not recognise a whale’s flipper as an arm, but if you examine the X-rays you will see that humans share the same kinds of bones.
The main difference is that a human hand has retained mobile joints, whereas the whale flipper has become a rigid, rudder-like paddle - excellent for powering through water.