If you are one of those people who have gluten intolerance, that is to say, celiac, and you want to go on a cruise, go ahead with it, no problem. On the boat they will take care of you and provide the food you need, as if you were at home. Most shipping companies already take this particularity into account food and indicate in all their buffets which prepared foods are suitable for coeliacs.
Also and just in case, you can point it out at the time of your reservation, so that if there are more passengers also with gluten intolerance they will put you at the same table.
However, and from your own experience, you know that it never hurts to comment on it with the waiter assigned to you, or with the maitre d '. You know that you should eliminate from your diet any product that contains trigol oats, barley, rye, spelled, triticale and products derived from them, but obviously you can take other types of food such as meat, fish, eggs, milk, cereals gluten-free (rice and corn), legumes, tubers, fruits, vegetables ...
The only thing that you should take special precaution, As if you don't go to a specialized restaurant, there are times when gluten-free foods are fried in oils where products with gluten have previously been fried, and the gluten remains in the oil.
For example the shipping company MSC Cruises offers exclusive menus for celiacs on the ships MSC Splendida, MSC Fantasia, MSC Magnifica, MSC Musica, MSC Orchestra, MSC Poesia, MSC Divina and MSC Preziosa, on the Mediterranean and Northern Europe voyages. These menus are served at breakfast, lunch and dinner. And for all destinations, all ships offer a selection of prepackaged gluten-free products on board. And they also have a store with special foods.