Killer whales sleep by floating motionlessly in the water for a period of 5 to 8 hours. Captive orcas may sleep by resting on the bottom of the pool or floating near the surface.
Killer whales do sleep with their eyes closed, just like people. However, newborn killer whales do not sleep at all. When a female orca has a baby, she may go weeks without any sleep.
The babies are constantly moving, so the mother must not only stay awake constantly, but she must also work hard teaching her baby to breathe and protecting it from predators. Dolphins also go weeks without sleep after giving birth.