Whales don't sleep the way humans do. This is because they are consious breathers: they have to remember to take a breath! Whales will half-sleep preferably vertically, either standing up or heads down. When in rest phase, the whale uses mimimal oxygen and a heightened lung capacity, which means a single breath could last for up to an hour! However, usually their naps are only 15-20 minutes and the whole group wake up simultaneously.