In the Navy, when in rough weather the cooks would put out sardines with mustard on them and saltines. Allegedly this was to help those with motion sickness keep something in their stomach - assuming you could gather enough courage to eat the danged things. Then there were those of us who felt it was a sick joke being played on us.
The ships will provide dramamine, but by then it is too late since you need to take the stuff before the motion sickness happens. Motion sickness really isn't a problem on most cruises and I think many people worry so much about it that they talk themselves into being sick.
Apples and looking at the horizon are effective.