My DD and I tried it on our recent cruise. I will say it helped. I am a little prone to motion sickness - so I was prepared with that, and also with Bonine. But I really did not want to use the Bonine - I knew it would knock me out (sleep), and I prefer to avoid medications if at all possible.
We seemed most troubled with motion sickness in the MDR's in the evening. We carried it in our evening purse and used it. I won't say it took it completely away - but it did help significantly. Then when dinner was over we could get outside, take some fresh air, and see the movement of the ship comparative to the water, or the horizon - and that is what helped the most.
Good luck!