We took a private ferry from Port Blair to North Bay Island(500/- per person). This beach had enchanting view of the neighboring islands and still water hence permitting all kinds of under-sea activities like Snorkeling, Sea Walk and Scuba diving. And yes, even when all 6 of us were great non-swimmers, we happily and successfully completed Scuba diving. We used the "Discover Scuba Diving" for 2800/- per person which includes the training, the diving, a CD with your pictures and video and a certificate. They provide you with the diving suit and lockers to keep back your stuff and don't forget to carry some extra clothes. Each person is offered a dedicated trainer and they are pretty good. I doubted my performance but they instill lot of confidence in you by saying "Ma'am you will forget everything after going down there, on seeing those colorful fishes around you" and yes that was more than true. They take you upto 12 metres deep for 30 minutes. You can get a small bucket of fresh water for 10/- after the dive but believe me you don't need it. The entire experience definitely cannot be put down in words. You got to see it yourself.