https://books.google.com/ngrams/graph?content=seasick&year_start=1700&year_end=2019&corpus=26&smoothing=1#

Why?

Boomers are one of the least sea sick generations in history, you gotta hand it to them.

The mid-20th century dip is in the early 70s. That's roughly when the dollar is unarmored from the gold standard, thusly turning the post-Bretton Wooods world seasick, adrift, rudderless.