That's what you do when you don't want the hassle of hauling them dirty to where you an wash them. It's the easily available modern substitute for banging the laundry rocks by the side of the river.
ummm they are not using cloth diapers, they are disposables. Instead of changing the baby and throwing them into the many available trash cans, they take the baby to the lake, strip it, wash its butt in the water and leave the diapers floating in the lake.