Although your cruise will provide some amenities it's best to pack the necessities you will need. If you forget something and are forced to buy it on the ship be prepared for a HUGE sticker shock, I once paid $35 for a bottle of sunscreen....ouch!
In Your Carry-On Bag
Make sure to have all your travel documents in your carry-on or purse so that they are easily accessible and won't get lost. Pack prescriptions in the original container in your carry-on. Also pack a small toiletry bag (keep in mind airline regulations on liquid sizes), a change of clothes, and a swimsuit. It is not uncommon for your luggage to be delayed in transit. Being able to slip on a swimsuit and wait poolside for your bags beats stewing in the lobby!
Full-Size Luggage
Wheeled luggage is best since some airports require you to deplane on the tarmac, while others feature long walks from the gate to ground transportation. Larger resorts can also be spread out, meaning a hike to your room if you're too impatient to wait for a porter.
In your checked luggage pack your regular-sized toiletry bag. Don't forget reef-safe sunscreen along with a first aid kit including the following items:
Tylenol Benadryl
Anti-nausea medication Imodium
Anti-itch cream Antacids
Pens Phone chargers
Roll clothes to prevent wrinkles. I find that packing cubes are great for keeping all your clothes together so that when you open your suitcase you don't have a landslide of clothes coming at you.
You'll generally need 3 different clothing categories for your vacation.
Casual: shorts, t-shirts, tank tops, sandals, running shoes.
Dressy/Formal:
Men - long pants (not jeans), collard shirt, closed-toed shoes
Women - skirts, dresses, nice sandals
Beachwear: swimsuits, coverups, flip flops, beach bag.
You may also want to pack a sweater or light jacket.
It's also a good idea to start packing early, this will give you time to slim down your options as one generally starts out with way more outfits than needed. Less will leave you room for souvenirs and you'll be thankful your suitcase isn't any heavier!