during a trip down the grand in 2002 our party had a flipped raft in lava. all the watershed bags on board were completely dry and all of the traditional roll down bags were soaked inside. coincidence, i think not. i've been an advocate of these bags for awhile, but a few words of caution: first if you buy one make sure you read the instructions on how to open them, sounds funny but you can bust the zippers on 'em pretty (scarily) easily. get some armor-all for the zippers as well. Second, baby the hell out of them too, they aren't made of the quality material like jacks plastic bags are made of.