Answer:
humans sleep while uncounscious, with inactivation of muscles (no conscious controll of the body takes place), and sensorial perception is strongly reduced, like smelling or vision.
Explanation:
A dolphin closes one of its eyes, opposite to the hemisphere he shuts down, and the other half of the brain takes the survival functions of breathing, monitoring or scanning the environment if any threats are to be considered.
When in the wild they normally sleep together with other companions. So they can protect themselves and monitor each other.
The constant need for air makes the dolpin go to the surface while spending the lowest energy by doing so only an hemisphere takes rest. Deep and slow waves process ocurr inside this cetaceans.
