This is the Tanana River in Nenana, Alaska. It's one of the Yukon's largest tributaries. I can break my usual "no naming rivers" policy for this picture because there's no fishing (except with bait for burbot) in the Tanana -- it runs with incredibly turbid glacial melt-water in which game fishing is pretty much impossible. You literally can't see an INCH into it, probably not even half an inch.
Troutnut.com is a collection of pictures and information about fly fishing. Fly fishermen, fly tiers, and trout enthusiasts of all stripes can learn more about life beneath the surface of trout streams, as well as how to better imitate aquatic insects with artificial flies to catch trout. There are aquatic insect pictures, underwater pictures, landscape pictures, and a comprehensive reference to the common names of trout stream insects.