Smaller quantities of ginger have at least some effect. When I was young I remember drinking a glass of ginger ale for an upset stomach and it had a very settling effect. That was Vernor's ginger ale which has a higher concentration of ginger than most soft drinks - more like ginger beer. On a recent Crystal cruise they served pieces of sugar-coated raw ginger as an after dinner digestive. It definitely helped people who were feeling a little queasy, though it was so strong it knocked out your taste buds for a while. Not a bad alternative to some of the drugs on the market though.
Be sure to test whatever medication you choose for side effects before you go. My husband had a bad (to us) reaction to Bromine, but we didn't realize that that was the problem until almost the end of the cruise. Consequently, his biggest memory of Alaska is feeling bad.
i have had good results with ginger. It works to settle the tummy and the slight queezies. You will see me with a glass of ginger-ale in my hands, especially the first couple of days, i haven't taken the pills, i like the ginger candy and gingersnap cookies, take it at first sign of the queezies and then get OUTSIDE into the fresh air. I don't know how it works on severe motion sickness. Keeping something in your stomach- even if its just crackers works well-sort of like the morning sickness cure