A couple of years ago, my husband and I went to an exhibition of George and Martha Washington's personal effects, etc. at a local museum. What I thought was interesting was they had a dress described as Martha's swimwear. Imagine a t-shirt made of woven fabric, rather than jersey, that extended from shoulder to the floor. The information card stated that Martha liked to take the waters at spas, so I suppose that would be like someone just sitting in a pool today. Considering that the Washingtons were what we'd call middle aged during the American Revolution, just the fact that a matron had a swim dress in her wardrobe tells me that it wouldn't be unheard of for a young lady like Georgiana to splash about.