As I said earlier, they do have a limit on personal water and they don't want it as part of checked luggage. Officially the Royal Caribbean policy still says personal beverages, both alcoholic and non-alcoholic, are not allowed with the exception of 2 bottles of wine per adult. However, the reality is the security at the embarkation ports don't usually care about a 12 pack or so of water or soda per person in the carry-on luggage. When you board a ship you go through screening similar to an airport with all personal items x-rayed and you clearing a metal detector. The same happens each time you return to the ship while on the cruise.
When you arrive at the ship on embarkation day, your main luggage has to be checked in with the porters. They put it in transfer bins, which are then moved to a screening area where ship's security is involved as they x-ray each piece. Luggage with questionable items, such as a lot of bottles, will be pulled aside. If unlocked they will open the suitcase. If locked they will call you to the security area on the ship to open it in their presence. If prohibited items are found they will confiscate them and return legal items when the cruise ends.
While most cruise lines set no weight limit for luggage, they do use the term 'reasonable amount'. Bear in mind the typical cabin is around 150-200 square feet including the bathroom and closet and you are responsible for storage of your suitcases in your cabin. Thus, one or two pieces per person is the norm. Many of us can pack for a cruise with just a carry-on roller bag and a small suitcase. I only use a carry-on for shorter cruises like a 4-nighter. Efficient packing.
Why would you want to bring food? Perishable items would be a problem. You can't bring fresh fruit aboard, or ashore from the ship. Against the law both in the U.S. and in most countries you will visit.