Lighter and less bulky than a traditional dry bag Outdoor Research HydroLite™ Pack Sacks feature a special waterproof finish that repels and blocks water molecules better than waterproof lightweight fabric treated with SilLite and other treatments. The cordlock closure helps keep most contents dry but if you're concerned with immersions consider doing a double-bag routine and buy two bags in the same sizes. These are excellent bags for paddling fishing and backpacking under swollen clouds.