I put anything I don't want to get wet in one of these and secure it under my kayak seat, where it fits perfectly. I tested it by putting a few pieces of tissue in it, submerged it about a foot and spun it around a couple of times underwater, and no leaks.I still put my wallet, phone and car keys each in a zip lock bag for redundancy, but my food, tools, etc., that you want to keep dry but aren't as critical, just get tossed in and have never gotten wet.