We have used Bonine in the past and it has worked well. My only suggestion is to take it the day BEFORE you sail as well as when you get on board. It will get into your system and once you've taken it for a day, you will get over the feeling of being sleepy.
I also have drank mint tea while on board if I get at all feeling a bit sea sick. I have also heard that ginger tablets work for some folks.