I tend to get car sick and just a little dizzy on boats (big and small). For the last Olivia cruise, which was very rough seas (unfortunately) as we were ahead of a storm front, I was very happy to have brought Meclizine and my favorite-Ginger caps. Whole Foods or any other store with natural supplements sell the ginger and I swear by it. On the cruise when it was less than comfortable I took 2 ginger pills 3 times a day and a meclizine in the morning and one at night if I was struggling. Never got sick, and the build up of meclizine in my system meant I was not tired after the second or third pill. Perhaps, consider pre-treating with the "sleepy pills"-dramamine, bonine etc. and get them to build up so you can tolerate and adjust to the sleepy effects!
As a side note--the TV Show "Mythbusters" did a special on motion sickness. The item that worked best for several of the participants who were put into different motion sickness producing situations, was GINGER. In the experiments they tried dramamine, the patch, and other remedies and many agreed Ginger was a top choice. Even though there is no empirical evidence of Ginger being a remedy, holistically many of my friends and family also enjoy the benefits of Ginger. I would personally say the only thing I don't like about the ginger is a little heartburn--but drinking more water when I take the pills usually solves that problem.
Best wishes and see you out there. We'll be on the 2nd 40th anniversary cruise and so excited to get away!