Interesting subject (seasickness) that's not talked about too much (except with whatever creature may be swimming by the side at the time).
Observation has led me to believe there are 3 categories that seem to cover everybody:
1) Never get sick regardless of personal or ocean condition.
2) OK with a patch, pill, or other remedy, but if too much partying, sleeplessness, or weather takes place, all bets are off.
3) Get sick looking at the water.
Most folks appear to fall in category 2. Personal research has led me to believe that too much party or too much time spent not sleeping are the main reasons why those groups get sick. Besides the obvious advice, any suggestions?