The Kitbrix bags are tough waterproof bags that will keep your stuff safe. You can join them together in a long line if you need to, or combine two into a backpack that also fits into the carry-on size for airlines.
They come (or did, see the note below) with mesh pockets on the outside, two waterproof pockets on the inside and a clear pocket in the top of the bag, as well as an ID card slot and high-quality strap.
Downsides: they are pretty expensive. They had some financial problems and had to restructure. Since then, the latest bag I purchased was not quite as good (missing a few features) but it was still essentially the same bag.
We use a simple one, two or three star rating system. One star for stuff we do not like, two stars for gear that is okay and three stars for equipment we recommend. We awarded this product 3 stars. All reviews and ratings represent our opinion only.