Sure, I'd be happy to help you plan your 3-day itinerary in Andaman. Here's a suggested itinerary:

Day 1:

• Start your day with a visit to the Cellular Jail, also known as Kala Pani. This historic jail was used by the British to imprison Indian freedom fighters during the colonial era.
• After the jail visit, head to the Corbyn's Cove Beach for some relaxation and water sports activities like jet skiing, banana boat rides, and parasailing.
• In the evening, attend the Light and Sound Show at the Cellular Jail. The show narrates the history of the jail and the struggle for India's independence.

Day 2:

• Take a ferry to Ross Island, which was once the administrative headquarters of the British in Andaman. Explore the ruins of the old buildings and the Japanese bunkers.
• After Ross Island, head to North Bay Island for some snorkeling and scuba diving. The island is known for its coral reefs and colorful marine life.
• In the evening, visit the Samudrika Naval Marine Museum to learn about the marine life and the history of Andaman.

Day 3:

• Start your day with a visit to the Mahatma Gandhi Marine National Park, which is home to a variety of marine species like turtles, dolphins, and dugongs. You can take a glass-bottom boat ride to see the coral reefs and marine life.
• After the park visit, head to the Chidiya Tapu Beach, which is known for its scenic beauty and bird watching. You can also enjoy a beautiful sunset here.
• In the evening, visit the local markets to buy souvenirs and try some local cuisine.

I hope this itinerary helps you plan your trip to Andaman. Have a great time!