Dolphins can be sea-water or fresh-water. They are found in all open seas and sometimes come into mouths of the large rivers. There are 32 types of sea and four species of river dolphins. Dolphins are able to jump highly out of water and to float very quickly under water. Emotions, including sense of humour are peculiar to dolphins. They have a sense of taste. As people, they can distinguish sweet, sour, bitter and salty tastes. The dolphin eats about 25-30 kilograms of fish a day. By means of "echolocation" dolphins can distinguish their relatives, and also metal subjects of the different sizes and structures.