I went on cruise ships in 2001, first ship as photographer, then photographic manger for the next couple. yeah its a good blast! conditions depend on the ship, but these days the conditions are really good as it is mostly new ships and there are strict protocols regarding safety and living quarters etc. you work a lot, and you have to be fast on your toes a lot, but you get to see some amazing places, thing is, you're a photographer, so your job is to photograph these people doing what they do in all the beautiful places they go to, which means you get to see them to, its your job. The company i used to work for has a couple of ships cruising the Hawaiian Is, good ships to work on. oh and there is approx 1500 crew. If you're interested or have more questions PM me, I can give you some very good contacts but you need to be serious about it first. it is definitely a ticket outa hell, I can vouch for that, but then i think that also depends on your attitude.
edit: just so you know, it is one of the biggest ship & resort photographic companies in the world, they put photographers onto many cruiseship companies all over the world, not just one. and there is always an opening if you're keen.