I will also endorse the Transderm Scop patches (also known as Scopolamine patches).
To be most effective, they need to be placed behind the ear at least 3 to 4 hours before setting sail. It wouldn't hurt to put them on around noon on embarkation day, depending on when the ship sets sail. They last for three days, and at the end of that time, the decision can be made whether to place another one.
Good luck and happy cruising!