Kind of odd, there's a real macho attitude around sea sickness ... "won't happen to me", "tough it out", etc. But when you think about it, nothing to do with toughness or attitude ... it's a medical condition, and it's way more common than people admit. From what I can tell, about 1/4 of people get it once the open ocean swells start. Or maybe more, if others in the non-chucking 3/4s are effectively medicated. I also know some guys with sea legs as strong as anyone that still get it once in a while, when doing the wrong thing at the wrong time on the wrong day.
I bet there's also age issues involved. Last summer I took my kids to the PNE, rode one of the spinning rides once, and had that light-headed dizzy feeling after...danger danger. I've never had that happen before, used to ride them over and over ... which my kids did, while I sat on a bench and watched (Old Guy). Same principle must apply to seasickness, as it's all related to equilibrium / eustachian tubes. For some reason, older people are less tolerant of that kind of motion. Add to that the fact that most of us indulge in beerz the night before and coffee the morning of ... that also doesn't help at all!