If you join a cruise ship for a few days, the safest thing is that the purchase is already made and all you have to do is present yourself equipped and ready to go. However, often the crew will go ashore to make the purchase, so these precautions are worth taking into account: Make sure you know if the skipper belongs to the school of canned goods or if you prefer fresh meat, fish or vegetables and make use of the kitchen on board.
Check if there is refrigerator on board and, if so, how big it is. Shop accordingly, avoiding buying too many delicacies that need to be stored with special care. Even when buying fresh food, keep in mind the cruise plans and opt for quick preparation and ease of eating. If you arrive at an anchorage at nightfall, a ready-to-eat meal will generally be more appreciated than a more elaborate one. Try to buy milk in cardboard or plastic containers. Glass bottles are a risk on board a ship. A fine burgundy or a claret often travels badly on board a ship. Reds from La Rioja are more robust when it comes to withstanding the rigours of life on board. If they are making short stages from one port to another and in each place they stay for a time, the purchase for a boat is not much different from that of a house. However, for longer stages it is vitally important to carry adequate food reserves to cope with possible emergencies. Any cruise ship should be able to cope with an unplanned night at sea, and yet every season there are multiple cases of poorly stocked yachts being trapped outside by an engine problem or something caught in the propeller. Normally, this type of incident should be an inconvenience rather than an emergency, but it can become a serious survival problem if there is only a packet of tea bags and some leftover food in the closet.