I get terrible motion sickness, and OTC medications (Bonine, Dramamine, etc.) do not work for me. Last summer, I took a cruise to Bermuda -- straight into a hurricane (Hannah, IIRC). Before pulling out of port, the captain warned of rough seas, so I headed right to the infirmary.

The doctors prescribed me Dilatin (since then, I have learned that Tegretol is also used for motion sickness). It actually worked. I still got slightly nauseous, but nothing like what I normally experience, and the ship was being tossed around like a toy boat.

Hope that helps...being sick is never fun, especially on vacation.