While there are other species of dolphins that live in brackish water (a mix of salt and fresh water), like the Irrawaddy dolphin, they are not considered true freshwater dolphins.
The Amazon river dolphin is the only known species of dolphin that has adapted to live exclusively in freshwater, spending its entire life in the Amazon and Orinoco river systems.
This unique adaptation makes the Amazon river dolphin a fascinating example of how animals can evolve to thrive in diverse environments.