Try crossing the ocean on a liner before the days of commercial jet travel.
Even Lord Nelson suffered from occasional seasickness.
Horatio Hornblower once got seasick in port.
Charles Darwin was seasick for almost all of the entire 5-year voyage of the Beagle. That he was able to do the work he did on that trip while suffering from seasickness is pretty amazing.
Scientists like him are practically extinct! 
… or get pregnant…
I think that’s the case. Having never been an astronaut nor even experienced the famous Vomit Comet™ or anything more than a roller coaster, I can only relate the few things I’ve read and related to.
Becoming weightless, or nearly so, is extremely disorienting for some short period of time, possibly just minutes – depends on the individual. The vestibular sensors in your inner ear that are attuned to motion and gravity go nuts in the absence of gravity, prompting nausea and even vomiting in some people.
There’s probably a correlation with susceptibility to seasickness. Most adjust to it eventually, as most qualified astronauts seem to, and regard floating around weightless as “fun”. But I can well imagine that some don’t.
I could get a woman pregnant in about 45 seconds. Tops.