You do not mention which cruise line, but as a general rule you will find you can get every meal via buffet on most of the larger mass market cruise ships (RCI, Princess, HA, Carnival, etc). But, I do not think the buffet food is anymore Kosher than the food in the dining rooms. Some cruise lines can provide Kosher food in the dining rooms, but its generally pre-packaged frozen dinners (not very good). Most of our Kosher friends find that they must compromise when they travel (especially on ships) and tend to stick with sea food offerings. But, for those who want to maintain a strick Kosher diet....I think they are basically out of luck.