Dang, you're quick to respond. B-) Yeah, I noticed that too where they did wear slippers in the water. Also, many did wear swimming caps or hats as well. Here are a few more from a French postcard, circa 1905:
Dibs on the blonde chick. B-D
We've established that Muslim women are about 100 years behind the times in swim wear. I guess the encouraging thing is that if we changed, so will they, eventually.