I started a similar thread years ago, you can see it
here. I was more focused on avoiding seasickness but there is lots of good advice there.
Avoiding seasickness is the top priority, if you are sick you will not have a good time. I have had good success with original Dramamine. I take the first dose at least an hour before we are scheduled to depart. I have only had to take a single pill every six to eight hours. You can take up to two every four hours, but the more you take the drowsier you can get. Some of the other medications are single pills with much longer dose intervals. With them if you are having some seasickness you can't immediately increase your dosage. If you plan on taking medication for motion sickness, I would recommend that you test it prior to your trip to see how you react to it.
An odd piece of advice that I got was to not bend over. I thought this was ridiculous at the time, but on the boat I bent over to access my backpack, next thing I knew my head was swimming and I was on the deck. Someone helped me up, I got the horizon back in view and I quickly recovered.
If you are in rough seas, avoid riding in the bow of the boat. It is typically smoother in the stern of the boat. Avoid the stern if you are smelling diesel exhaust.
Eat light and frequently and keep hydrated. Don't eat anything greasy or hard to digest but do eat. Ginger ale can help with an upset stomach.
Make sure that you have plenty of water, not just to drink, but to rinse any salt spray from your waterproof optics.