If I don't take precautions, I'll be throwing up all day at sea.
I use Primatour. I take one pill before I go sleeping, still at home. I take another pill when I wake up just before driving to the boat (a one hour drive).
Doing so has worked for me up to 1,5 meters of swell. I don't notice any fatigue or sleepiness caused by the pills.
If I have a "bad day" I try to lay down with my back on the deck of the boat, close my eyes, keep eating and try to sleep.
Trying to get some distraction also seems to work.
Good luck,
Anton