The correct answer is Gangetic Dolphin.

• The Gangetic river dolphin is India's national aquatic animal and is popularly known as ‘Susu’.
• Dolphins are one of the oldest creatures in the world along with some species of turtles, crocodiles, and sharks.
  • The Ganges river dolphin was officially discovered in 1801.
  • Ganges river dolphins once lived in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems of Nepal, India, and Bangladesh. But the species is extinct from most of its early distribution ranges.
  • The Ganges river dolphin can only live in freshwater and is essentially blind.
  • They hunt by emitting ultrasonic sounds, which bounce off of fish and other prey, enabling them to “see” an image in their mind.
  • They are frequently found alone or in small groups, and generally a mother and calf travel together.
  • Calves are chocolate brown at birth and then have grey-brown smooth, hairless skin as adults.
  • Females are larger than males and give birth once every two to three years to only one calf.
• It is among the four freshwater dolphins in the world- the other three are:
  • The ‘Baiji’ now likely extinct from the Yangtze River in China.
  • The ‘Bhutan’ of the Indus in Pakistan
  • The ‘Boto’ of the Amazon River in Latin America.