Dolphins have inspired many poems, myths and legends over the centuries. The appearance of dolphins alongside a vessel's bow has long been regarded as a good omen, and these charming, friendly animals probably attracted the interest of the first men that ever sailed the seas.

The common dolphin, Delphinus, is found in all seas, but is most plentiful in warm and temperate waters. They leap gracefully through the water as they overtake ships travelling at 18 knots or more. Some dolphins have been reported travelling at speeds of around 30 knots.

Dolphins are mammals and bear a single baby at a time, after a gestation period of 11 to 12 months. The infant dolphin is born in deep water, and must reach the surface almost instantly to breathe. The mother dives underwater to help the newborn to the surface, however the baby can reach the surface under its own power.

Members of the dolphin family include:

• The Killer Whale, Grampus (Orcinus)
• The False Killer Whale or Little Killer Whale, Pseudorca
• The Pilot Whale, Blackfish or Caaing Whale, Globicephala
• The White Dolphin, Sotalia
• The Spotted Dolphin, Stenella
• Risso's Dolphin, Gramphidelphis
• The Bottle-nosed Dolphin, Tursiops
• The White-beaked or the White-sided Dolphin, Lagenorhynchus
• The Black and White or Skunk Dolphin, Cephalorhynchus
• The Irrawaddy Dolphin, or Water-squirting Dolphin, Orcella
• The Right Whale Dolphin, Lissodelphis

Most dolphins are sea creatures, but there are a number of groups of river dolphin, familyPlatanistidae, to be found in southern Asia and tropical South America.

Dolphins in Art and Culture

The earliest known portrayal of dolphins in art is in a collection of ancient images carved into rocks in northern Norway. One of these is estimated to be around 8,000 years old. A few centuries later dolphins appeared as motifs on vases, coins, mosaic floors and in paintings and sculptures. An early example of this is the fresco of a dolphin on the wall of the Queen's room in the Minoan palace of Knossos on the island of Crete, which is estimated to be around 3,500 years old.

Many ancient cultures, such as the Aborigines and the Greeks, traditionally regarded dolphins as spirits and messengers of the gods. There are many tales of dolphins allowing people to ride on them. Pliny, the Roman writer, tells of a dolphin which had a great affection for the son of a poor man and carried the child to school each day in Peteoli and home again in the evening.

Dolphins Help Humans

There is evidence that they have special healing powers that cannot be explained. There are many accounts relating to the benefits of people spending time in the water playing with dolphins. Close contact with dolphins has been seen to alleviate cases of chronic depression or anxiety, enhance recovery from life-threatening diseases and speed up the learning potential of children with disabilities. It has been shown that contact with dolphins can help children with learning difficulties to learn four times quicker than any other teaching method. The children also retain the information for a longer period. It is believed that 'dolphin therapy' gives the children more confidence in their own abilities. It is hard to tell whether the person is healed by the dolphin itself or whether it just an effect of the emotional uplift of seeing a dolphin close up.

People say that dolphins are beautiful, intelligent creatures, yet not enough is being done to save them from extinction. Dolphins have paid a large part in our history and, hopefully, will continue to do so.