In summary
dont drink the night before and get enough sleep
dress appropriately---not too hot, not too tight, not too cold
take one tbl in the eve and one before eating in the morning (I think Kwells is best)
no big breakfast, just a little snack
on board: dont sit in the cabin---ideally stay and stand outside---better balance
eat all the time little things like musli bars
try to talk and chat away, keep busy
dont sit down and tie lengthy rigs.
Seasickness is 90% confidence (or loss of). If you get seasick once, you have a huge chance to get seasick again---and if you have been on board a few times without seasickness, you gain confidence.
However---even after hundreds of trips without seasickness, I have seen guys getting sick and could not believe it! Nobody is safe.
That is why I stick to those (easy) routines and reccommend them for any allday fishing trips.