Dolphins: Social and Playful
Dolphins are often regarded as one of Earth’s most intelligent animals. They are also very social and can establish strong bonds like staying with an injured, even helping them to breath by bringing them to the surface if needed. The «Moko» Dolphin in New Zealand has been seen protecting a swimmer from sharks by swimming circles around him.
Play is an important part of Dolphins culture. Dolphins enjoy riding waves and surf swells. If we are lucky, the bow waves of boats. At times leaping between the dual bow waves of a moving catamaran.
They generally sleep with one brain hemisphere at a time only to maintain enough consciousness to breathe and to watch for possible threats. Would be quite convenient for sailors too!
More Infos:
Wiki
National Marine Mammal Foundation
Ted Video «Dolphins as persons»