I've been on the Navigator of the Seas, and the sofa bed in our room was a bit of a mystery too. From what I saw, it does open up and fold out into a double bed. It’s not the plushest option but works fine for a night or two. If you’re looking for something more comfortable, I found a great resource on wooden wardrobes – they had some nice pieces that might make your room feel cozier if you’re using the sofa bed a lot. On our trip, we just made do and it was okay for the short term.