For how big the island is... I would imagine it to be, 

The island we are currently on is four times bigger than the city of, New York and then transitions to another island. 
[img]http://www.drodd.com/images13/new-york-map1.jpg[/img]
Since this is all of, New York x4 there would be an abundant amount of islands that people would use ships or whatever mechansim to get across.