When Sperm Whales(Physeter macrocephalus) sleep they take a deep breath, dive down about 45-65 feet and lineup levelled perfectly vertical. These massive marine mammals sleep sound and still like this for about 7 percent of their time taking short (6 to 24 minute) rests in pods of 5 or 6 whales. These brief naps might be the only time the whales sleep. Untill 2008 no one knew whales slept vertically until a study documented this behavior.
