As you get closer to the equator, you are exposed to more UV radiation. Plus during the cruise, you are likely to be spending more time outside then you do at home which also exposes you to more sunlight and more UV radiation.
Do not forget to buy some sunglasses for the trip. I recommend bringing a few pair that way when you accidentally leave a pair behind at the bar, you will already have another pair ready for you when you get back to your room.
Sure, you can buy sunglasses on the ship but then you are at the mercy of the limited selection available. Buy your sunglasses in advance to guarantee that you have the style that fits your face and personality.
