Dolphins are mammals in the order Cetacea. They are part of the toothed whales. Generally, they are among the smaller whales. Most live in salt water oceans, but some live in rivers - there are oceanic dolphins and river dolphins. Dolphins are from 1.5 to 4 metres (~5 ft to 13
ft) long. The Killer whale is the largest of the
group, and can be about 8 metres (26 ft).
The name 'dolphin' comes from the Ancient Greek δελφίς (delphis) meaning "with a womb",
because it was first thought to be a fish with
a womb. It is now known to be a mammal, and quite an intelligent
mammal. Dolphins breathe air. A dolphin's nose is
on top of its head so the dolphin can easily breathe on the surface of the water. The skin of a dolphin has no scales. It is soft and
smooth. However, it is very firm, due to how much muscle they have. Dolphins
useecholocation to find their food.