Neat island, but I can assure you South Americans and Africans would have no issues invading it by boat.

It would be a decent stronghold though for awhile I bet, but in the end desperation would lead to its discovery and pillaging.

Have you ever played the game rust? It's a survival game where the world you spawn in is pretty large. It always amazes me how similar people think in survival games. No good spot ever goes undiscovered.

If the islands were not mapped that would be your best bet.