Not to be a killjoy, but there is no cure for seasickness. Conversely, *everything* cures seasickness.
Do you know why?
Seasickness is all in your head. Seriously, it's your brain feeling motion but not seeing a cause for it and going wonky because of it. It increases your heartbeat and your breathing and slows down blood flow to your extremities.
That is what causes nausea.
The best way to fix this is to distract yourself, or convince yourself there is no problem. Harmless placebos like magnetic bracelets and such are perfect for this; if your brain is convinced there's no problem, then you won't feel it. If you feel your heartbeat speeding up, try to slow it down. If you start to breath rapidly, try taking deep, calming breaths.
Seasickness is a fascinating study in self-caused distress and cures. Here's a paper NASA wrote about it dealt with spacesickness in astronauts:
http://http://spaceresearch.nasa.gov/sts-107/resourceguide/content/science/senses/info/k-4info.pdf