I get very seasick very easily. I get sick in cars, planes, and boats. I get sick in rocking chairs and porch swings. I get just a wee bit queasy in elevators.
Having any food in my stomach makes it worse. I cannot eat before going on a boat or while on it. Ginger does nothing for me, nor do the bracelets, either the ones that apply pressure by means of a little bead, nor the ones that give a slight electrical shock.
Original Dramamine does nothing for me.
Meclazine helps a little. That's the ingredient in "non-drowsy" Dramamine and in Bonine.
Scopolamine helps the most. I'll still get a little queasy in moderate seas, but not enough to spoil the fun. In severe seas I'll get sick, but less sick than without it.
The scopolamine patch (Transderm Scop) seems to deliver too much scopolamine the first day, increasing side-effects, which can be severe, and for me consist of a sore throat and some dizziness, and delivers too little the third day (it's supposed to last 3 days) so that I get sick. Maybe the seawater affects the delivery of the medicine.
So I've switched to the scopolamine tablets (Scopace) which have to be taken every 8 hours, but can be split in half and taken in dosages from half a tablet to two tablets, and repeated at intervals from 6 hours to 10 hours, allowing you to fine-tune your dosage. This seems to work best for me.
Scopolamine should not be taken if you have narrow-angle glaucoma or even if you have narrow angles that have not quite become glaucoma. It can decrease the angles and cause an episode of over-pressure in the eyes. (There is a procedure involving a laser that can reduce eye angles, so narrow angle glaucoma is not a lifetime prohibition against scopolamine.) For men, scopolamine should not be taken if you have enlarged prostate. There may be other counter-indications as well. This is why it's a prescription drug. Taking someone else's prescription, or giving some of yours to someone else can have serious medical consequences, including permanent eye damage in the case of glaucoma.
As many people have said already, it also helps to stay hydrated (though it can be difficult once you are already sick), to stand amidships, and to watch the horizon or a point on land, if visible. Standing and holding onto the boat allows you to move as the ship rolls, thus reducing the total actual movement of your upper body. That is, you want to move contrary to the boat's motion, thus minimizing the motion of your upper body.
I hope this helps.