I don't get actually sick, but I have the thing in the shower
people talk about, and in general feel uneasy on land after a long spell at sea.
I have never been seasick, and I actually crave the motion of a lively seaway. I love the way it feels; I need it, my body needs it, actually. I have been in the backseat of a jet trainer doing aerobatics, and never felt a twinge, much to the amazement of the pilot. But ex-Royal Navy
submariner friends of mine say that there are conditions where no one without exception can avoid seasickness; I just haven't experienced them. Maybe.