The correct answer is option 2, Ganges River dolphin. The Ganges River dolphin, also known as the South Asian river dolphin or Susu, is the National Aquatic Animal of India. This unique dolphin species is found in the Ganges-Brahmaputra-Meghna and Karnaphuli-Sangu river systems in India, Bangladesh, and Nepal.

Let`s take a look at the other options to understand why they are not the correct answers:

Option 1, Gharial, is a critically endangered crocodile species that is native to the Indian subcontinent. While it is an important aquatic species, it is not the National Aquatic Animal of India.

Option 3, Dugong, is a marine mammal also known as the "sea cow". It is found in the coastal waters of the Indian Ocean and is known for its herbivorous diet. Although it is a fascinating and important species, it is not the National Aquatic Animal of India.

Option 4, Smooth-coated otter, is a species of otter that is found in South and Southeast Asia, including parts of India. While it is a charismatic and important aquatic mammal, it is not the National Aquatic Animal of India.

In conclusion, the Ganges