1) Havelock Island, Andaman
2) Neil Island, Andaman
3) Port Blair, Andaman
4) North Point, Cinque Island, Andaman
5) Corruption Rock, Andaman
6) Grand Island, Goa
7) Netrani Island, karnataka
8) Kovalam, Kerela
9) Bangaram, Lakshadweep
10) Coral Sharks Reef, Pondicherry
From my personal experience i'd say reefs of Lakshadweep Islands are the best and then it's Andamans.
I have quite a friends who are in this Business.
Happy Travelling :)