When Akbar called Kashmir "Heaven", he definitely has not visited these islands!
If its diving to witness the ruins of the world war, or to experience swimming with the fishes 20,000 leagues under seas, or just cruise in the virgin mangroves, which lead to an unheard phenomenon of mud volcanoes! Andamans is full of surprises.
Port Blair, the capital, is mainly used for stop-overs or to just spend the night before venturing out to other parts of this archipelago. Nevertheless, while you are here, do visit the notorious Cellular Jail, narrating the saga of these islands during the Indian independence through a magnificent Light and Sound show.
Another things to see here would be the Japanese bunkers, constructed at Corbyn's Cove during the World War II, and while you are here, stroll across the beach and do try the Pani Puri flavored ramen from the beach-side shack. There are changing rooms and umbrellas available at a very minimal charge.
Then probably start your journey by taking the three island tour from Aberdeen Jetty. In this tour, one is taken via ferry to North Bay, Ross, and Viper.
Ross Island was the first capital during the British era, and in all these years, due to earthquakes and tsunami, only one-third of the island is left. Nevertheless, it still holds the ruins from the British reign, and holds magnificent stories. One being of how the British experienced skin diseases, leading to deaths of many, due to the ground water, while the locals bathed in the same without any effect. While there, look for the tour guide for more such stories and amagnificent experience of dinning with the wildlife. While here, please do not feed the Bambi looking deers or any other animals.
To get a glimpse of North Bay just look behind the 20 rupee note, it holds the split vission of this island. One usually comes here for all the water activities, be it snorkeling or just a simple water-scooter ride.
Viper island witnessed the execution of women freedom fighters during the independence, the ruins of the women jail still bears memories of the same.
Other things to see while in Port Blair are: Chidiya Tapu, Nariyal Bagicha (you would need army clearance to enter this beach full of coconut trees).
A drive through the Jarawa (indegenous tribes) territory leading to Baratang. Here lays the boat ride through mangroves and swaps, giving an experience of the boat ride through the Amazon rainforest, leading to the prestine limestone caves. A 25 mins boat ride from Baratang will take you to the unheard phenomenon of "Mud volcanoes", which are active.