I drank with Bonine and didn't have a problem. I *can't* say I wasn't affected a little, but it was more like a little "buzz" - certainly not incapacitating.
Lots of folks swear by sea bands, but I wouldn't count on them 100%. They work for some, but not for others. Bonine will work and hopefully not make you drowsy.
I suppose if you *know* you are prone to motion sickness you might want to start dosing yourself before sailing, but I decided to wait and see. I didn't feel sick AT ALL, even though I did feel motion. I only took the Bonine when the seas got to 20 feet and then not because I felt "sick", but just a little lightheaded.
Carnival Elation March 11
Carnival Imagination Sept 07
Carniival Sensation Dec 06
RCI Sovereign of the Seas Sept 06
Carnival Miracle Sept 05
Carnival Glory Sept 04
Carnival Fantasy Jan 04