I am very prone to motion sickness. WHile the new, huge ships have very little movement, even there I can have a problem. So, I take ginger daily and if I start feeling just a tad dizzy, which, for me, is the very first hint of motion sickness, I take a meclizine. I carry them in a pocket.
One thing not mentioned here is that if you have ports where you have to tender into shore, using the smaller boats, you can run into a lot of motion, so on those days, I take the meclizine 1/2 hour before I get on the tender.