They wuld be even slower underwater, and something would eventually add them to the chain food.
And zombies have to eat, they would have a rough time getting to an island.
And the island I would choose would be one with rocky borders (not one with a nice beach, sadly), so that it would be nearly impossible for a dumb, slow zombie to get into it.
Zombies would never become part of the food chain. A zombie transmits its virus through bite, why is this? cause zombie tissue is saturated with the zombie virus, deadly to animals and humans, but will cause reanimation in people. If you accidentally ingest zombie blood, or zombie tissue most likely you are gona die and reanimate.
This is also why zombies dont decompose very fast, the bacteria, and scavengers that would normally make short work of a corpse either die on contact or avoid it at all cost. This is the reason why a zombie apocalypse is even feasible and does not only last for a couple weeks, cause they dont simply rot.
Zombies don't eat persay contrary to what popular culture says about zombies and brains. They instinctively "eat" people because biting is how they transmit the disease.
An elevated island would be great of course providing that you could be self sufficient once you climb to the top. I'd imagine that an island with rocky borders and only one easily defensible passage up would be pretty perfect. The chances of zombies washing up onto the island are pretty slim in any case, so i think that you would be safe.
Edited by frostz, 22 May 2011 - 02:25 PM.