https://dev.bukkit.org/projects/ships This plugin adds the ability to create fully functional ships, airships and submarines, pilot-able through simple sign controls. Most ships require coal to move. Since it is sign based it has no impact on server performance.
This plugin definitely seems cool but doesn't exactly fit with the theme of our server. As a goal, we have always tried to keep our server as close to the roots of vanilla Minecraft as we can. Of course, we have plugins, but plugins only to create more community engagement and prevent griefers from destroying your hours of hard work. However, this is just what I think about it and because we want this server to be as community run as possible, I'll continue to keep my eye on this thread to see what others think about it. If it gets an overwhelming amount of support, I'll definitely test it and add it. It may not be compatible with claiming which may cause players to grief and enter territory claim owners don't want players to though, but we'll see.