Which of the following is called the 'Tiger of the Ganges' along with the distinction of being the 'National Aquatic Animal'?

Option 1 -> Ghariyal is a critically endangered fish-eating crocodile found in Indian rivers, but it is not the National Aquatic Animal.

Option 2 -> The Ganges River Dolphin (Platanista gangetica) is India's National Aquatic Animal and is nicknamed 'Tiger of the Ganges' due to its position at the apex of the aquatic food chain.

Option 3 -> Royal Bengal Tiger is a terrestrial mammal, not an aquatic animal, though it is India's National Animal.

Option 4 -> Hippopotamus is not native to India and is not found in the Ganges river system.

Hence, Dolphin -> The Ganges River Dolphin was declared India's National Aquatic Animal in 2009 and is called the 'Tiger of the Ganges' because it is the top predator in the river ecosystem, indicating a healthy river system -> correct