I just double confirm with my friend who just stayed with this property last week. He told me the returning boat transfer was indeed free of charge. As for the arriving boat transfer, he was not sure if it's free. Naka Island offered him a promotion which included airport pickup, by BMW 7serises, and arriving boat transfer for 1800THB ++ which I consider as a good deal. If anyone is thinking of going to Naka Island, this promotion is highly recommanded.