Barely adequate is the best way to describe this. I had a West Marine branded dry bag that had a fairly thick waterproof lining and worked great for at least 2 years. When that got beaten up enough to be retired, I went back to West Marine, but all they had were these sea to summit bags. More money, less dry. This bag is not completely waterproof in constantly wet conditions, the lining is just too thin. It doesn't hold air either, one of the nice features of my old bag was it would float if you sealed air in, definitely a nice last resort safeguard. This one is a shriveled mass in 10 minutes or less. It's dry enough for my wallet and key fobs, but definitely not for a smartphone. Sea to summit makes some cool products, I have a packable backpack that is quite useful (but you sure do pay for it), but this is an expensive disappointment. I won't be buying another.