How long is a piece of string? It vaies enormously. I have travelled on this ship several times across the Bay of Biscay and only once has it been rough. The English Channel was even worse on that occasion. It is the luck of the draw. If passengers are seasick the medical department on board have treatment which will resolve the problem.Think positively and I think you will be fine. Enjoy your cruise.
Try Avomine tablets(available off prescription) Boots chamist will probably say "never heard of them" but if you persist and ask the pharmacist to look them up, they can order them in for you. Take before you travel and for a a couple of days into your cruise, Take again if rough weather threatens. If you hit any really bad weather and feel seasick head off to the medical centre the moment the seasick feeling starts and have a phenergan injection. It is something of a miracle worker, but the key is to have the injection early. Dont think "I will wait and see if I feel better"--you wont, once the symptoms have started.
The best thing i have taken for seasickness is traveleeze you can buy them in boots the chemist and they are strawberry flavour chewy pastilles. you take 2 and they work for 24 hours they are brill. i wouldnt cruise without them.one bad weather day i had people knocking my cabin door to ask for them. just try them.