Scotia Prince is a passenger ferry, which has been doing Maine-NS cruises for a number of years. They tried making it a Fla-Bahamas ferry in the winter, but the idea just didn't catch on. Just off the top of my head, it's not as well-equipped as a regular cruise ship, but it doesn't have to be. And if you are in the habit of using a TA, please do ask
her/him about this - it is bookable both direct and through TA's.