We cruised with cunard on the qm2 and there was never a chance of getting seasick. BUT just in case they have a doctor on board who will give you an injection which will avoid i.
I also suffer from sea sickness. The first cruise I went on I had to see the doctor and have an injection, which makes you sleepy. For the rest of the cruise I was completely fine. On my second cruise I took some pills that my local pharmacy recommended and I was OK, just a little queasy for the first day. But it has not put me off. I think after a day you get your 'sea legs'. Hope this helps.
I get extremely travel sick too - but I love cruising. They can give you an injection on board, which makes you sleepy, but I find over the counter tablets called "Stugeron" work a treat (and I've tried several different types until I found this one). Although the tablets make you sleepy, you take them just before you go to bed - so you get a great night's sleep too, and usually the next day, you're in port, so you don't need to take one. Also, because you start taking these just before your cruise sets sail - you don't end up feeling unwell. I've tried the wrist bands and ear clips too (natural remedies), but found these of no use at all. I cruise twice a year, and since taking the Stugeron tablets, have never been ill..... the only place I advise you to avoid is the Bay of Biscay - so if you're going to the Med - do a fly cruise - so you get all the fun, but none of the illness. Don't be put off - if someone had told me about Stugeron earlier - I wouldn't have had the problems I had for the first 3 cruises I did!!!!!
I agree with the use of Stugeron, it got me through 17 hours of gales up to force 10 . I never even felt sick although we were confined to the cabin (and our beds) and were very uncomfortable. I was on them at the time for vertigo, the doctor gave me them. Take them and enjoy your cruise.