Dolphins

• Life hack: they are able to sleep with half of their brain

Dolphin is a common name of aquatic mammals within the infraorder Cetacea. In general, this term refers to the extant families Delphinidae, Platanistidae, Iniidae, and Pontoporiidae, and the extinct Lipotidae.

So, in order to avoid drowning and detect predators at the same time, they sleep with only one brain hemisphere in slow-wave sleep at a time. This process is known as unihemispheric sleep. For example, they close the left eye to rest the left brain hemisphere and vice versa. Living in water, they have to swim continuously and consciously to avoid any potential danger and injury. So, sleep episodes last between 4 and 60 seconds.