I have been sea sick since I was 2 or 3 years old, but I love the ocean. I have been sick on about every charter boat out of westport and illwaco, even in the calmest conditions. I have puked so bad at the canadian princess they came in early, even though I wanted to keep fishing, the guide called me hard core.
It may have been the swells combined with the diesel smell, but I found a cure.
I bought my own 30 ft. twin gas engine boat, I bought gravol from a canadian store, and I troll.
At Swiftsure and La Peruse Banks I use downriggers on the bottom and troll 2.5 - 3.0 mph. I catch Halibut, Lingcod, Kings and Silvers all on the bottom. With the boat always moving and the Gravol taken the night before and that morning I felt great. Probably owning my own boat and having to pay attention helped me never even get sleepy.
So buy a big boat, always troll, and take Gravol. It worked wonders for me. ( I told the wife it was a Yacht, now I have to take her on trips to Nanaimo and Cambell river so she can tell her girlfriends she spent two weeks on her yacht. Don't you dare tell her it's a fishing boat. My friends are amazed my wife picked out a 30 ft. boat for me so I wouldn't get sea-sick.)

Ken