DUBAI, United Arab Emirates (CNN)–If you’ve ever dived into the ocean and come across giant sperm whales floating vertically motionless, you should know that these whales are sleeping.

So the American submarine Susan Bird decided to document the scene while it was off the Caribbean island of Dominica. (Watch video above).

The question remains as to why sperm whales sleep vertically.

There are many theories as it may be related to their body composition and the presence of a waxy substance in the head area, which is lighter than the density of muscles and bones. bodies.

So she may be more comfortable sleeping this way, and it may require less effort for her to float upright.

A vertical nap may be more difficult for predators to detect from below because it represents a much smaller mass than a horizontal one on the surface.

Sleeping upright helps relieve water retention.

These whales face many threats, especially: shipwrecks, seawater pollution and fishing.

Sperm whales, found in oceans around the world, have complex communication skills that set them apart from other groups.

Speaking to CNN in Arabic, Beard said: “Her beauty is surreal… She’s huge but unnaturally calm. It’s impressive to watch her as she sleeps upright.”

Bird observes the behavior of sperm whales to educate people about the beauty of these marine creatures and inspire them to protect their valuable habitats.