Think Gomez think.....
The Island should be as far away from Tamriel as allowed by Oblivion. It should be surrounded on all sides by some form of carnivorous fish...ill have to make a visit to the imperial library to find a suitable one. It should be high enough level to deter players from trying to swim back; some way has to be devised to keep resourceful alchemists and cunning mages from trying to levitate or water walk back though.
All in good time.
now off to study up on my zombie logic!