I think they stay on because of the "rubbery" part touching the bottom of my foot. Hard to explain, but they do stay on, and I do not use the strap behing my foot. My feet are average width and they do seem to be swimming in the shoes. My teenaged girls don't like the way they fit, but I do. Not sure if I would were them at WDW though, my feet do get hot in them. I prefer socks and tennis shoes for long, hot days of walking.