I have used them once while hunting to make waterproof leggings to cross a shallow river during winter. Just pull them over your boots and tape them as high as possible to your legs with duct tape. They may spring a small leak where you step down on sharp rocks and stuff but if you walk fast only a little water gets in. The thicker the bag the better they work for this. This worked out so well for me that I always carry two spares just for this purpose anywhere that I may need to cross shallow water while afield.