I've cruised in the Gulf in Nov/Dec twice and both my son and I got violently ill. Even the crew said the weather and seas we experienced both times was really bad, though. From my experience, nothing stops the seasickness once it sets in (except the boat reaching calmer waters). But there are a few things you can do to prevent/minimize it. If the boat is rocking and you start to feel dizzy or nauseous, get out from the interior of the ship where you can see things moving. Get out into a deck where you can get fresh air and look at the horizon (which isn't moving). The more you focus on things moving back and forth, the worse it gets. I couldn't even keep Dramamine down. For me, the worst thing I did was go to the room to try to "sleep it off". Ginger does relieve nausea, but if you're already really sick, it takes a while to have any effect. I also found relief in the hot tub. Something about the heat and sensation of the water jets distracted me from being dizzy and disoriented.
With that said, the worst part of the cruise was in the Gulf. Once we got to the Caribbean, the waters were much calmer and we had no issues at all.