Not most. A lot of the islands are fairly large, most people live there. Though, people do say we're living in the Age of Pirates, because so many people have set sail to find the pirate king's treasure in the past 20 years. So, all of those people, as well as many marines, do effectively live on ships, I suppose.
[Law just keeps accidentally making his world sound more and more exciting. That said, he does notice You seems pretty taken with it.]

Are you interested in sailing?