4. North Sentinel Island, Andaman Islands
The island is small and covered in greenery but the coral reefs around it make it difficult to reach on water vehicles. Helicopters may have been able to access the remote island, but the obstacle, in this case, is not the environment of the island, but its inhabitants. They reject outside contact fiercely. Their tribe remains cut from the modern world and lifestyle and they intend to keep it that way. The Indian government recognized this fact and banned anyone from visiting this island. And that is probably for the best because the Sentinelese people since their immune system is not capable of fighting against modern diseases.