Here is a great tip, Ginger Capsules, which can be found in any vitamin store or Target/Walmart work like a charm. Take 2 a couple times a day and you will not have any problems with sea sickness. I am super prone to motion sickness and using a combo of the transderm patch and ginger keeps me feeling absolutely great. I could probably go without the patch but i can't even turn my head fast without getting dizzy :-)
Try it and you will see . . . no side effects and it works great. The only thing is, bring a big bottle. I passed out many to anyone not feeling up to par and they all felt better.