#1 The cruise ship is heavily air conditioned. I packed only "cruise-clothes" (i.e. tank tops, sandals, and shorts). This can make for a miserably cold vacation.
#2 The cruise line sent us documents stating that we could only have one small suitcase per guest. They gave dimensions that you could not exceed, so we didn't. But pretty much everyone else brought huge suitcases filled with everything they needed.
#3 Sunscreen and aloe cost $12 per bottle on the ship, so bring enough of both with you.
#4 You can bring empty water containers with you and fill them up with fresh water on the ship to take with you on your excursions or travels at port.
#5 It can get pretty boring on the ship. It's harder than you think to have no responsibility. You can easily run out of things to do, so pack plenty of games and reading materials. And go to as many of the activities that are offered on the ship. It's fun, free entertainment.
There are so many things to think about before you leave, and it's hard to get it just right. We had fun on our trip but if I had known these few things I would have had a much better time.