Kabuki, Bonine and Dramamine are non-prescription medications. Bonine is better, in my opinion, because it does not make you drowsy. If you have kids though, they cannot take Bonine (also sold by the brand name Dramamine II) but they can take a half tablet of regular Dramamine.
I have tried the scopolamine patch (prescription required) and it is very effective. Unfortunatley, there can be side effects as well. I tried it on one cruise years ago and had some drowsiness and dry mouth. It was better than throwing up though, so you have to decide what your priorities are.
I have taken one Bonine tablet every morning of our last two cruises and even with a few days of 12-foot seas, I felt fine and had no side effects. I would recommend Bonine, available over the counter at your local drug store. On board, they also have generic Bonine tablets at the Medical Center and at Guest Services that are free for the taking.