I get it bad, real bad. I was in the keys doing my nitrox cert. We spent alot of time trying to hook up to a ball that was 10' down, and I ended up getting sick before the dive. Then the seas were pretty rough, and the surge from the waves was felt a good 20' down, so during the safety stop I was feeding the fish. Then after I surfaced, and on the way back in.... My dad was in the dive shop afterwards, they didn't know he was standing there, and he heard them say, "he's a great diver, but man, you need a firehose for afterwards.." for some of us, it's a fact of life, and one you'll just have to accept and learn to minimize.
Afterwards, I learned to hydrate for at least a day prior. Many experienced divers I know use Triptone, and that helps me considerably. 2 before bed, and 1 the morning of, or if it's a night dive, 2 befor lunch, and one a couple hours prior to the dive. Stay away from alcohol the night before, if at all possible. Fruit works well, an apple seems to be a pretty good breakfast. Lots of water. Don't zip up your wetsuit till the very last minute possible, the restriction around your neck can trigger the queaziness. Did I say lots of water?
Even doing all of this, sometimes in nasty seas, you still might do the technicolor yodel, but you won't turn green and fall to the deck a limp shadow of a man. You'll bounce back and be able to make the rest of the day. I second the ginger snaps, and ginger ale. If you're doing ok, then sometimes pretzels help soak up some of that sloshing in your gut. The thick pretzels, not the thin ones.
Island Hopper boats.. stay away from Island Hoppers... They are a specific type of boat that is well suited to be a dive boat, except for the round bottom. They roll and pitch in perfect harmony with the long-wet-yawn... Many charters in Florida use them... Stick with deep V hull boats if at all possible, they sway and roll less.
Good luck and pray for science to come up with a vaccine, or an operation, or a procedure, or a shot, or genetic engineering... something for the love of god!!!! hehe
Jason