Humpback whales (Megaptera novaeangliae) lobtailing, Icy Strait, Southeast Alaska, USA.
Humpback whales are the most acrobatic and playful whales on the surface, making them the perfect whale for whale watching, with the additional bonus of their spectacular cooperative bubble net feeding behavior. They engage in a lot of breaching (jumping) and lobtailing, which is when they raise their flukes out of the water and slap the surface repeatedly as this individual is doing. It creates a thunderclap noise that can be heard miles away. Actually on this occasion it was a cow and a calf lobtailing together, and the calf is often the instigator for play: they kept this up for about half an hour. There are many possible reasons for this behavior including trying to dislodge barnacles and other parasites, communicating with other whales, herding prey and as a threat display to boats that approach too closely. It could also be just for recreation.