Get some organic cotton balls. If you are right handed, put a cotton ball in your left ear, if you are left handed put a cotton ball in your right ear, this helps some people with seasickness.
Hi Debbie, Ginger tablets are brilliant but the secret is to take them 30 mins before boarding. I see no reason why you could not take fresh or powdered ginger. Some comercial opperators on boats offer ginger tablets on boarding. These help some but for most people it works best if taken 30 mins before you board. You can top up with them onboard. I forget the recommended intervals but you do need to take them more than just the initial dose.