Dolphins

Dolphins are one of the intelligent animals on earth. Dolphins live in a water body, however, they are not a fish, they are mammals. Dolphins can't breathe air in the water like other aquatic animals, they need to come to the surface to breathe air. They have a blowhole on the top of their head through which they breathe. 

Dolphins have excellent hearing and eyesight. They generally use echolocation inside the water to locate their food.  Dolphins have a 'signature Whistle' which allows other individuals to recognize them.

There are many kinds of dolphins around the globe. The largest dolphin is the Killer Whale which can have size more than 20 feet long and weight up to 4 tons. While the smallest dolphin is the Heaviside's Dolphin have the size just over 3 feet long and weighs up to 80 to 90 pounds.

Dolphin's half of the brain sleep at a time. When one half sleeps the other half is awake and keep dolphin from drowning. They may also float at the surface while sleeping.

Dolphins are social animals. They live in groups and cooperate with each other. They are very sharp minded and easy to train. Dolphins are trained for rescue missions. Dolphins are very friendly with humans.