Flora and fauna
In March/April (best time to go there) its generally very hot and humid. But the scenic beauty and landscape will soothe it. Do wear sunscreen and sunglasses. Also wear a cap. You can carry an umbrella while you walk.
You can also pay the local fishermen to take you on day trips to mangrove creeks (Bridget Creek is nice) or places like Mt Harriet National Park (where you can beach your boat and go birdwatching). Don't pay more than Rs 2000/day for the boat, and you can often bargain it down to much less. Be sure to check with the Forest Dept before heading out, as many destinations require certain permissions.
Walking is the only option. Its a small island.
See the British era quarters, clubhouse, offices as well their complete setup, which would include power station, water distillation plant, workshop, bakery (this is very famous), secretariat, church, ferar beach, old jetty, open air theater.
Also do see the Japanese bunkers.
You will find a lot of deer/stags in the forest over here.
There is an aquaguard in the jetty. Also you will get a lot of coconut water (Rs 15-20)