I can say that I've tried everything.
Dramamine (Meclizine), Bonine, ginger in all the ways you can think, burned a little "oregano", gone out on an empty stomach, full stomach, etc.
The only thing that has ever worked for me is Scopolamine (the patch that goes behind your ear). Yes it used to be offered here in the USA as a pill but no longer.
Does it work, you betcha! Does it have downsides, you betcha.
I place it behind my ear the night before I go out, and I wake up in the morning with major cotton mouth. It dehydrates me big time, even to the point of a little mild constipation, which actually isn't so bad for long days on the kayak. The biggest downside that I experience is it basically burns my skin. I'll get off the water, remove the patch, shower, and I'll have a raised red bump where I had the patch. Within a couple of days, it'll scab over, and a couple days later, that'll fall off. I even put lotion on the area for those couple days.
Each patch lasts for 3 days, and they recommend switching ears with every patch. They say don't cut the patch, but I used them whole and it burned my skin very badly, so now I cut them in half or even in quarters. The cost is also quite steep. They retail at $17 each, and with my insurance, I pay $7. My brother through his employer gets them for $1. Yup, a buck.
The potential conflicts with other medications are many, which is why it is only available with a prescription from your doctor. In higher doses than the transderm patch releases, it's a mild hallucinogen, but they sometimes give it to folks coming out of surgery, and are still under heavy anesthesia, to keep them from vomiting.
Here's a link to read about it...
http://en.wikipedia.org/wiki/Scopolamine
The stuff is wicked, but it works. I would try every other option before it, but in the end, it just might be the only thing that will keep you on the water, and not puking in your lap.
Hope this helps.