The Indus river dolphin is almost blind. Its eyes are tiny and only see light and dark. Instead of using its eyes, it sends out little clicks of sound and listens to the echoes that bounce back. From the echo it can tell where a fish is, how big it is, and which direction it is swimming - even in muddy water where you couldn't see your hand.
It is sometimes called the 'blind dolphin' or 'Bhulan' (its name in the local Sindhi language). It usually swims on its side, with one flipper stretched out underneath touching the riverbed - a bit like an animal feeling its way down a corridor with one hand on the wall.
These dolphins grow to about 2 metres long. They like the deep pools where the river bends. Females have a calf every two years, and the calf stays with its mother for about a year, learning where to find food.
Only around 2,000 Indus river dolphins are left in the world. Pakistan has set up special protected stretches of the river just for them, where boats slow down and people watch out for them. It is one of those rare animals that lives in only one country, anywhere on Earth.