You will probably hear many different opinions, but the formula used in non-drowsy Dramamine works fine for me. If you have a tendency toward motion sickness and have not been cruising before, take a dose an hour or so before you sail, but unless you are extremely sensitive, you will probably not need it at all unless the seas are 7' or more. In any case, it's good to have some on hand, if only for peace of mind! If you wait to take it until you are already quite queasy, it won't be as effective; I have used it if I know the seas are rough (take one in 24 hours) or if I start feeling just a bit "off" in semi-rough seas, and have had good results.