A fashion plate from Le Supreme Bon Ton, circa 1810-1815.
This is the earliest depiction I have seen of people wearing what appears to be a garment made specifically for swimming. People have obviously gone swimming for millennia, but until the mid-19th century or so there was no specialized garment for the activity and participants usually wore their undergarments or nothing at all.
It is also interesting as it shows men and women swimming together while in various states of presumably scandalous undress. But then it again it was post-revolutionary France, so who knows.