Reverse Tail Slap

This is a view from below the ocean surface of a female humpback whale (Megaptera novaeangliae australis) turned upside-down, slapping the water with her peduncle and fluke, i.e., rear end.

humpback whale fluke slap
Humpback whale reverse tail slap (License image)

Quite the sight to behold, and the percussion to hear/ feel.

There are probably many reasons why humpbacks do this. In this instance, she was engaged in activity with her calf, who was off breaching, slapping and practicing other important baby-whale stuff.