Feelfree Gear's unique Track waterproof backpack design offers two closure systems. When you don't need the waterproof membrane, you can simply remove it by pressing it against the inside wall.
Then fold down the cover. Your backpack is waterproof. In a water environment, take out the inner membrane, roll it up twice and clip it on. Then fold the cover down and your backpack is 100% waterproof. The front pocket, equipped with reflective stripes, will allow you to store a water bottle and a wet towel for example.