For cruises traveling to international locations such as Jamaica, Mexico and the Bahamas, you will need to bring along identification. If there is only one thing you remember, it is this. A passport will be needed, as well as other state-issued identification, such as a driver's license or state ID. If you forget your passport, you may not be let off the boat and into the country, which would defeat at least part of the purpose of traveling on the cruise.
If you are headed for warm weather climates, you will need to pack accordingly. Shorts and t-shirts are practically a given, but make sure to throw in some casual dress attire into the suitcase. You will be having dinner with other individuals and you'll want to appear at least somewhat put together. You'll want to bring at least one swimming suit, as well as any other swimming equipment you may need (goggles, ear plugs, head cap, etc.). You should also bring one sweatshirt or sweater, just in case. Nighttime at sea can get a little chilly (as well as breezy). It may also get a little chilly on land if you are there during the evening or nighttime.
For cold weather cruises, follow Carnival's recommendations.
All of these items will be available on the boat, but you'll pay an arm and a leg for them. Toothpaste, toothbrush, deodorant, soap and shampoo are extremely important. Also make sure to bring along some sunblock because you will be in the direct sunlight a great deal. Bug repellent may also come in handy. It rains often in the Caribbean, which can make it muggy and oftentimes perfect for different insects. Protect yourself with some strong bug spray (DEET is often the best and most effective).
A small case of medication will also come in useful. Tylenol, Pepto Bismol and sore throat medicine will come in handy. Hopefully you will not need then, but you never know (and remember airline regulations regarding liquids).
