The Union Territory of Andaman and Nicobar Islands consisting of about 293 islands (39 of which are inhabited) is situated in the Bay of Bengal .

ENTRY FORMALITIES : 
Overseas Nationals: Foreign tourists require the ‘Restricted Access Permit’ is issued on arrival at Port Blair by the Immigrations and the same does not need to be applied in advance. However guests need to make sure that there is no ‘Entry to Restricted Areas Not Permitted’ on their Visa stamps. Guests need to declare that they are visiting these Islands during visa issuance process. This process ensures that there is no separate stamp stating ‘Entry to Restricted Areas Not Permitted’.  If this exists, do contact the Indian mission to amend the same.

Hotels typically are not responsible and do not adjust payments or amend reservations to account for any issues related to Restricted area permits. So guests have to make sure that the ‘Entry to Restricted Areas Not Permitted’ is not there. 

Kindly do not confuse 'Entry to Restricted Areas Not Permitted’ with ‘Not valid for prohibited, restricted and cantonment areas’. ‘Not valid for prohibited, restricted and cantonment areas’ is a pre-printed separate line applicable for military zones and has nothing to do with Andaman Islands..

Indians: Indian nationals need no special permits to visit Andamans. 

HOW TO GET THERE?
Air: Port Blair is connected by Indian Airlines, Jetairways and Air Deccan with Chennai, Kolkata and Delhi. This is the preferred way to reach Portblair.
Sea: Regular passenger ship services viz. M.V.Harshavardhana, M.V.Akbar and M.V.Nicobar are plying between Port Blair and Madras (1190 km), Calcutta (1255 kms), Vizag (1200 kms). This is not preferred mode of transport as it takes two days to reach Portblair.

From Portblair, Havelock Island is accessible by a Ferry and the timings are as under:

Note: 

Hotels - There are limited rooms in Port Blair and Havelock and so prior reservation is an absolute must. The way ferries and flights timing mismatch, transit accommodation at Portblair at least once and in most cases twice is required.

Flight - Port Blair Airport is closed after 2 PM everyday. Therefore all Flights are scheduled during Morning to early Afternoon Hours. Flights are not co-ordinated with ferries for onward journeys and So all itineraries with Havelock Island have to be designed keeping 1 night at Portblair each way in Transit (As 2 PM Portblair - Havelock Ferry is small and so getting tickets is not always a certainty). Flights tend to go full during Season and to be booked well in advance.

Season

Peak Season - Winter - Dec and January (Best time)
High Season - Winter - Oct, Nov and Feb,March (Good time)
Summer Season - April-May (Hot and humid)
Low Season (Monsoon) - June to September (Unpredictable weather)