Every time I need to go on a boat ride, I convince myself I'm not going to get sick and every time I do get sick. I've always hoped that it would be something that I grow out of but I never have. I guess my inner ear is not shaped that way.
The difficult part is remembering to take the nausea medicine in time. If you don't take it at least three hours before your trip, it doesn't work.
Since the trip I'm usually taking is about three hours long, simply forgetting the medicine beforehand has made me miserable more than once.