For our first cruise we used Boots Own sea sickness tablets. We were reccommended to start taking them 48 hours before travelling and to continue them for the duration of the cruise. This worked well even though we had some very rough weather.
This time we are trying what the Americans rave about. Transderm Scopolamine is a prescription only medication administered via a skin patch you wear behind the ear.It lasts about 72 hours and then you replace it with another patch. The advantage is that it is not just a treatment but also prevents you getting sea sick in the first place. I had a chat with our GP and she knew it immediately, even saying it was what she and her husband always used themselves. Obviously it will not suit everyone but it might be worth asking about.
Try one of the seasickness remedies available over the counter, they are usually effective, also the travel bands (available from Boots at about £6) are helpful, but with a bit of luck you shouldnt need anything, most of the time you dont even realise you are cruising it is so smooth.
My Granddaughter gets a patch prescribed by her doctor the Americans seem to use these all the time,its placed behind the ear but it works well but can have side effects. RCI will give you sea sick pills at the pursers desk but P&O you pay at the doctors or buy over the counter stuff.As said before you will probably not need them as you will get your sea legs after a couple of days .
Got seasick on the costa marina we were provided with tablets and they were amazing worked very quickly able to have our evening mea.
Try Avomine tablets(Boots Chemist probably will not stock them but can order them in for you) They are the most effective over the counter remady I have found(and as I have balance problems after an illness I am a bit of an expert!!) If these fail you(they may in really bad weather) then get down to the medical centre ASAP(the moment you begin to feel seasick) and get the medic to give you a Phenergan injection. You will be feeling better in the time it takes to return to your cabin(Yes, really as quickly as that!!
Would also reccommend going on the larger ships 70000 tons upwards as they seem to be more stable in bad weather.
if all else fails, as Setter say , get the injection it works very wel.
Hope it will be ok March as im going to med on Costa Serena dont like it rough but we are in Spain already so should be fin.