Granted this is a good idea finding a little known island and setting up base there for these reasons #1. Zombies are few and far between in the middle of the ocean granted there may be a few stragglers that manage to make to your island fort since zombies don;t breath they will follow you under water they can walk under the water for a few days but are thankfully to stupid to swim so the only way they can get to the surface is by floating up and that can happen when zombies become water logged (like a piece of warped wood) then they can pull you off the side of a boat while its anchored down. Back to the main topic having your stronghold on an island is hard to get started but once it gets running they usually flourish because due to the good climate you can grow all kinds of fruit which can be a main source of food until the infection has cleared out. The one down side to this is most people have probably thought about this before you and may have inhabited the island as their own. My next post will elaborate on this.