Which of the following is recognised as the National Aquatic Animal of India, symbolising the need to protect river ecosystems?

Introduction / Context:
National symbols are frequently tested in competitive exams. India has designated various national symbols to highlight important aspects of its natural heritage. The National Aquatic Animal was chosen to raise awareness about river conservation and endangered freshwater species. Knowing which animal holds this status is essential for environment and civics related questions.

Given Data / Assumptions:

• The question asks about the National Aquatic Animal of India.
• The options list different aquatic animals, including crocodile, sea turtle, dugong, dolphin and a popular fish.
• We assume the symbol refers especially to a freshwater or river associated species in India.
• The correct option should represent an officially declared national level symbol.

Concept / Approach:
India has declared the Ganges river dolphin, a freshwater dolphin species, as its National Aquatic Animal. In many exam oriented questions, this is shortened simply to dolphin. The declaration emphasises the need to conserve the Ganga and other river systems. Although salt water crocodiles, sea turtles and dugongs are important aquatic animals, they have not been chosen as the National Aquatic Animal. Therefore, among the given options, the generic term dolphin points to this official symbol.

Step-by-Step Solution:
Step 1: Recall that India selected a freshwater species as the National Aquatic Animal to highlight river conservation. Step 2: Remember that this species is the Ganges river dolphin, often referred to simply as dolphin in general knowledge questions. Step 3: Examine the options and identify dolphin as the only entry that directly matches this national symbol. Step 4: Note that salt water crocodile, sea turtle and dugong are marine or coastal animals and are not used as national aquatic symbols in India. Step 5: Choose dolphin as the correct answer, understanding that it specifically represents the Ganges river dolphin in this context.

Verification / Alternative check:
Standard lists of Indian national symbols clearly mention Ganges river dolphin as the National Aquatic Animal. When simplified for MCQs, the answer choice is usually written as dolphin rather than the full species name. Crocodile and turtle appear in other contexts but not as the national aquatic emblem. This consistent pattern in exam manuals and environment notes confirms that dolphin is the correct option to mark here.

Why Other Options Are Wrong:
Salt water crocodile is an important reptile species found in Indian coastal waters and estuaries, but it has not been declared the National Aquatic Animal.
Sea turtle is a protected marine animal under various conservation programmes, yet it does not hold this specific national symbol status.
Dugong is a threatened marine mammal in Indian waters, important for seagrass ecosystems, but it is not designated as the National Aquatic Animal.
Hilsa fish is culturally and economically significant, especially in eastern India, but it has not been chosen as the national aquatic symbol.

Common Pitfalls:
Candidates sometimes confuse national symbols with species that are simply famous or endangered. Another pitfall is to mix up the National Aquatic Animal with other conservation mascots or flagship species from individual campaigns. To avoid these errors, it is useful to memorise the core list of official national symbols and keep in mind that the National Aquatic Animal of India is the Ganges river dolphin, represented in options as dolphin.

Final Answer:
The National Aquatic Animal of India is the dolphin, specifically the Ganges river dolphin.