It's not the same as a time share ownership, but I believe there is a cruiseline out there that the staterooms are actually PURCHASED (just like you would purchase a condominium on land).
That would be AWESOME if
DVC were able to build it's own Cruiseship to purchase DVC ownership on!! But, I wouldn't even want to think about how much THAT would cost to purchase!!

OR how many points it would take to book a stateroom.