How old is your baby?
I brought my 13mth old baby on Royal Caribbean cruise in 2010.
For breakfast it's bread and at the breakfast buffet, there'll usually be porridge. I would store the porridge in a thermal flask which I would then feed at lunch with egg or other things I can find at the buffet. I would usually "wash" it in hot water so that it's not so salty. Sometimes I can't find anything good to feed, then I would feed him food from baby jar or cereal.
Overall it was a very fun experience. My son enjoyed the cruise alot.