The best cure for seasickness is catching Fish! If im fighting a Fish, I forget about how sick and crappy the swell is!
on a serious note, I used to stay up all night, (not a morning person) so that i could get up on time to make it to the launch with the rest of the crew. Also I wouldnt eat anything, or even bring fluids. Id seem to feel uneasy in rough water, and very uncomfortable, but never at a puking stage. (long range trips i get very sick, whats wierd is when i was a kid i never got seasick)
Sometimes just getting a goodnights sleep, a good stable breakfast and lots of green tea on the yak works great for me.
Only time i get sick is when im not facing land. position your yak torward the land, and it will help alot.