Tigger,
I've gotten sea-sick on every cruise we've been on, but it's usually only for the first day. I know that on our last cruise, rough seas caused both my wife and I to leave dinner before we could get to dessert. But after spending the rest of the evening in bed, I was fine for the rest of the cruise.
In the past, we've used dramamine. We'd make the mistake of not using it until we'd start feeling sea-sick that first night. Then we'd do two dramamine to get over the initial sickness, then decrease to only one over the recomended interval for the next day or two before we'd drop using it all together. The only thing I don't like about it is that it makes me sleepy and I'll find my self unable to stay away while we go to a movie or something.
I think for our next cruise, I'll try to take some dramamine (one pill) around the time of the life boat drill, them MAYBE one the next morning and see if I can to fine without it for the rest of the trip. I've never had to continue using dramamine thru an entire cruise and usually don't after the first two days unless we encounter unusually high seas.
But again, sea-sickness has never spoiled our cruise. It's usually caused a head-ache (never vomited from sea-sickness). The only time I was misirable from sea-sickness was during an excursion. We were on a boat taking us to snorkel at some spot that was in open sea water with rought waves. The boat was tossed around enought that I was thrilled to get off of it and in the water to snorkel. But after about 15 -20 minutes, the water was rought enought that I had had enought of even that. I spend the rest of the hour snorkel time spralled out on the deck, eyes closed, chomping down some dramamine (again, starting it AFTER I needed it, not before) and prayed that I didn't vomit.
Just plan on taking along some dramamine and asprin and expect to feel a little woozy the first day until you get your sea legs, then enjoy the rest of the trip.
In terms of giving you an idea how much you should worry about sea sickness, I'm prone to motion sickness when I'm in any vehical (boat, plane, car) unless I'm the driver. I've had sea-sickness on EVERY cruise we've ever taken (about 5 Disney Cruises). But the sea-sickness is minor enough that we leave for a 7 day in two months, we're booked on a 14 day repositioning cruise, and fully expect to rebook another 7 day cruise while on board. Keep in mind, this isn't a small ship that gets tossed around (like the excursion boat where I did almost vomit on). It slowly rocks and you have to give your self a little time to get used to it.