To solve this problem, we need to identify the National Aquatic Animal of India from the given options.$\newline$Let's analyze each option:$\newline \bullet$Option 1: Gangetic shark - The Gangetic shark is a species found in the rivers of India, but it is not designated as the National Aquatic Animal.$\newline \bullet$Option 2: River dolphin - The River dolphin, specifically the Ganges River dolphin, is recognized as the National Aquatic Animal of India.$\newline \bullet$Option 3: Blue whale - The Blue whale is the largest animal on Earth, but it is not the National Aquatic Animal of India.$\newline \bullet$Option 4: Sea-horse - The Sea-horse is a marine creature, but it is not the National Aquatic Animal of India.$\newline$Based on the analysis, the correct answer is Option 2: River dolphin.$\newline$Therefore, the National Aquatic Animal of India is the River dolphin, which corresponds to Option 2.