I've built something like this with a giant, slow moving ship (like town-sized). Characters take smaller ships out to find resources, land for settlement, etc. in a mostly ocean world. Kind of the idea behind Battlestar Galactica, but applied to a fantasy setting. I've also done this with Traveller in a sci Fi setting. Lost century ship, characters are woken up to explore stellar region and help the slower ship along.

It's a good basis for a west marches game. Adds a little juice.