One of the interesting things to do in Port Blair is to explore the colonial heritage of Ross Island. A ferry takes you to this former capital of the British in the Andamans, which then became a colony of Japanese prisoners of war. It’s fascinating to see an old British church, now in ruins, and the remains of once splendid examples of British architecture. A few structures have been restored, and they certainly recreate the feel of a bygone era. You can also view the relics of Japanese bunkers, many of which were constructed at different spots on the Andamans.
Ross Island also has a beautiful beach and a charming museum.