Clad (Late-1700s to 1800s)
If you didn't see the water and the sand, you'd never know Victorian women were at the beach.
Modesty was, to put it mildly, a virtue, and it helped distinguish the gentility from the lower classes. Accordingly, an upper class woman's bathing suit (which was the only kind, considering the time and money it took to get to the beach) left everything to the imagination. It was, at first, a long "bathing dress," complete with weights along the hem so it wouldn't float up and black stockings to prevent show-through.
There was also, at some resorts, a small, fully enclosed room-on-wheels called a "bathing machine" that carried women from the fully-clothed shore to the water-costumed water, so they were never seen in swimwear by male bathers.
The Victorian-era suit went through a few changes -- at one point it was something of a jumpsuit, a one-piece, wool trouser-and-shirt set -- until the 1800s came to an end. At this point, the bathing suit starts getting (somewhat) functional ...