I originally purchased these bags because of their thin material, silnylon. I assumed it to be no better or worse for keeping my gear dry as I've never had a dry bag failure while seakayaking, even when there was water in my hatches. But the other day I went ww kayaking for the first time. The Sea to Summit got fully submerged for at least 10 full minutes in a rapid (the kayak was caught in rocks and filled with water). I was surprised that the dry bag kept all my clothes completely dry. The only reason I give the bags a 9/10 is because this will be my second season with them, and durability is still in question. If I'm still using the same bags by the end of 1 more season after this one, I'll raise the grade (if I remember to).