There is no direct flight from India to Santorini. The best way to reach Santorini from India is to fly to Athens and then take a connecting flight to Santorini.
The easiest way to get to Santorini is to fly. The airport is located on the island and there are many direct flights from all over the world.
There are no waterways connecting Santorini to any other island or mainland.
There is no public transport on Santorini. The only way to get around is by taxi, renting a car or motorcycle, or using the services of a tour company.