I love Magpul DAKA pouches. They are built like a brick shithouse, work well, and look great. However, they are expensive and because they are zipped, they are not 100% waterproof.
If you need something to stay absolutely dry when submerged, similar functionality otherwise, and a lower cost solution… well, check out these resealable Stasher silicone bags. While they might not look the business, there is no arguing their functionality.
Details here.
And if money is burning a hole in your pocket, but you still need something absolutely submergible, Nite Ize recently introduced their new RunOff Waterproof Pockets in a number of different sizes and colors. These things are priced similar to the DAKAs, but use a different kind of zip system that allows them to be completely waterproof.
I haven’t used or seen these, but initial reviews are really good.
Details here.