Humpback whales are often pictured actively swimming or leaping out of the water. Just like humans and most other animals, however, these large marine mammals apparently also need to take some rest and sleep.

It may appear difficult for these animals to sleep and manage not to sink in the water, but experts explain that marine mammals need to retain control of their blowhole through which they breathe air while they sleep so they do not drown. Researchers believe that cetaceans, such as whales and dolphins, should be conscious and alert enough to be aware that their blowhole is at the surface.

Unlike humans who can breathe even when their conscious mind is asleep, humpback whales breathe voluntarily so they need parts of their brain to be alert when they snooze so they can remember to breath. Researchers believe the marine mammals do this by shutting off only half of their brain at a time when they sleep.

"Humpback whales breathe voluntarily, unlike human beings. Since they have to remember to breathe, researchers believe humpback whales sleep by shutting off half of their brain at a time," explained the Animal Planet.

Interestingly, whales still manage to dream, or at least that's what some experts believe. When whales rest on the bottom, they would exhibit sudden twitches or contractions. These are also characterized by eyelid movements that indicate the possibility that they may be dreaming.

How exactly do humpback whales look when they sleep? You can watch them snooze in a video uploaded on YouTube by a research dive team known as Panga MX, which captured a humpback whale taking a peaceful nap.

"During a research project throughout January to April 2014 we encountered a sleeping humpback whale and managed to get an in-water encounter with her," related team member Kieran Bown who shared the footage on YouTube. "This is a short clip of a 20-minute encounter showing her come up to breath and check us out."

The video catches the humpback whale sleeping upside-down albeit marine mammals are known to remain in other positions when they sleep. Other whale species drift horizontally, a behavior called logging. Sperm whales also sleep vertically near the surface.

Brown said that the creature was sleeping peacefully and silently when they chanced upon it.

"The whale was completely at peace in the water and remaining silent," Brown said. "We floated and observed getting a great look at the giant."

Watch the video below:

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