I am sure we have all spent half a night pondering just how to dolphins sleep. Dolphins, being air-breathing mammals do need to surface, regularly, to breath in air which would pose a problem for sleeping! Dolphins are able to achieve this by having one side of the brain sleep at a time. So while the right half is sleeping the left half stays awake and allows the dolphin to swim, surface, and breath. After about 20 minutes the left side wakes up and the right side goes to sleep.