I've noticed an interesting anomaly regarding 19th century bathing/swimming costumes - while the fashionable silhouette changes dramatically from 1860 to 1880, the changes to bathing outfits is much less obvious.
The most obvious changes are seen in the trousers and the sleeves. Trousers become noticeably slimmer and shorter. Sleeves also become shorter. In the fashion plates, skirts sometimes disappear - it's hard to know if this happened in the real world.
We all know that what works in "Fashion World" doesn't always work in reality - the slipper below is a good example; while it's terribly cute, it would never remain on while in the water.
These caps don't look like they would be very practical either.
This slipper might at least stay on your foot, but I can just imagine what all those bows would look like when soaking wet.
Some aspects stay the same - a definite nautical influence in both trims and colors.
Just like now, some of these fashion plates show ensembles that seem better suited to lounging on the beach, rather than taking to the water!