Lots of people pay good money for exfoliation treatments—removing their dead skin. But some humpback whales take care of their own treatments. They strip away dead skin and parasites by rolling in the sand on the sea floor.

Scientists discovered the spa treatments when they studied three humpback whales, in 2021 and ’22. They attached instrument packages to the backs of the whales. The packages included high-def video cameras and sensors to record depth, temperature, and other conditions. After a few hours, the packages released and bobbed to the surface.

The whales were in Gold Coast Bay, off the eastern coast of Australia. It’s a place where humpbacks rest and socialize before and after their summer migration to Antarctica.

The cameras recorded all three whales dropping to the bottom of the bay. They nosed into the sandy bottom, then slowly rolled over—either on their sides or all the way onto their backs. Each roll took half a minute or longer, with the whole “treatment” lasting up to five minutes. In addition, one video recorded a companion humpback also rolling in the sand—a possible competitor with the first whale for female attention.

The researchers noted that the whales need to clean their skin to remove barnacles and other parasites, and to clear away infection-causing bacteria. The humpbacks can do some of that at the surface, but not all. The sandy “spa” treatment may complete the job—making the whales fit and shiny before and after their long treks to the Antarctic.