I am sharing my experience about my South Andaman trip (Port blair & Havelock Island), I traveled along with friends.
On reaching Port Blair Airport we took taxi to reach our hotel, but before reaching there we asked driver to take us to the Booking counter from where we can book fairy tickets as we have to leave for Havelock Island next morning. The driver was a good person he advised us that we should book Private Ferry Tickets as there are very less chances to get Govt. Ferry tickets (which proved right later in) otherwise we would waste a day of our trip and also said that we can get return ticket of Govt. Ferry, then he took us to agent for Booking and we booked Three tickets at rate of Rs.1525 per head (tickets need to be booked in advance to ignore the hustle). There was only 3 slots were left, somehow we able to save one day of our trip. After that we reached our hotel.