@largerben you have made some very clear and useful points, but there are also other tribes like them who at one time of the order were nearly wiped out from the surface of the earth because of epidemic out breaks and the civilized world had to wave in to resure them by giving them mordern medicines even when they had herbal medicines at their disposal.
Secondly no matter how good one can swim, I don't think one can survive a tsunami. If you ask me I think the sentinelese tribe are mysterious humans or what do you think?