Which one of the following is the national aquatic animal of India?

The Gangetic dolphin (*Platanista gangetica*) was officially designated as the National Aquatic Animal of India in 2009 because it serves as a vital indicator of the health of the Ganges river ecosystem. While the Gharial is another iconic freshwater species found in Indian rivers, it does not hold this national status, and the Olive Ridley turtle is a marine species primarily known for its mass nesting on Odisha's coast. This question tests the candidate's knowledge of India’s national symbols and the conservation status of key flagship species.