How many different freshwater dolphins are there in world?

There are four species of freshwater dolphins in the world:

1. Amazon River Dolphin (Inia geoffrensis)

2. Bolivian River Dolphin (Inia boliviensis)

3. Ganges River Dolphin (Platanista gangetica)

4. Indus River Dolphin (Platanista minor)

These dolphins are all critically endangered due to habitat loss, pollution, and accidental capture in fishing nets.