According to this book: https://www.amazon.com/Sea-Civilization-Maritime-History-World/dp/140004409X
Easter Island is is farthest island away from any other landmass.
I'm halfway through The Sea & Civilization right now. The scope is amazing and it's a scrumptious read. http://www.amazon.com/The-Sea-Civilization-Maritime-History/dp/140004409X