Bought 2 of these this summer for a self-support whitewater kayak trip on the Selway river in northern Idaho. I stuffed sleeping bag in one, and clothes in the other and they worked perfect. The bags are lightweight and waterproof, easy to close, and kept my stuff nice and dry even when sitting in puddle of water all day. I did not try to submerge them. I would be cautious about the long-term effects of abrasion on the fabric from sand within the hull of a kayak, but expect these will be great for wet-weather backpacking trips and long ski tours. Narrow size is great for kayak hull or backpack.