I think it affects people differently. Body make up and so on. I've been on the salt and in boats all my life. Only times I felt sick or got sick was when I was quite young and then when I was late teens early adult, due to stupidity of staying up all night drinking thinking it would be no problem with 2 or 3 hrs of sleep. In those two stroke days I wouldn't even get past the launch with all the exhaust before starting to feel it. These days its the 2.5 to 3.5 chop with tight waves that just constantly pound the boat. I feel it in my head mostly. Not physical just tiresome of that constant pounding. Aging sucks.