When you look at a river, what do you see? A few flies on top? A fish or two?

Look closer.

Lay down on your chest at the side of the river and stare down into it. Look at a rock or a stick. Not very interesting? Keep looking.

Soon, you begin to notice things that don't seem to belong. Sticks don't come with little tubes of sand attached. What's that black bump? Oh, it's moving. It's... grazing? Every stream holds a tiny alien world, packed with creatures unlike anything we see on land.

Clinging mayfly and stonefly nymphs graze like tiny cattle on the algae and microscopic animals that cover every twig and rock. Sinister damselfly nymphs hunt them with a creepy, deliberate stalking posture reminiscent of both a prowling cheetah and killer robots from the future in some cheap sci-fi flick.

Caddisfly larvae build intricate houses of tiny stones and debris, which the tiny carpenters drag around with them like a shell. Colonies of them gather on various twigs and rocks, little housing subdivisions in a tiny underwater town.

Swimming mayfly nymphs, some of them shaped much like the slimy villain in the Alien movies, dart from place to place with the deftness of little minnows and take up station to catch food drifting by in the current. And below the ground, burrowing mayfly nymphs dig lairs with their powerful tusks from which they emerge only at night to prowl for food. All hope to avoid the gaping jaws of a big, ugly, prowling dragonfly nymph.

Until now, it was hard to observe this underwater world without getting very cold and very wet. But a new website, Troutnut.com, has brought detailed photographs and videos of this intriguing world and its residents to the comfort of your computer desk.

The website was sparked by the sport of fly fishing, in which trout anglers craft realistic imitations of tiny stream creatures from an intimidating mess of fur and feathers, and present their imitations delicately, even artistically. For them, better pictures of the real thing mean better imitations and more trout. But Troutnut.com's quest for more and bigger trout has led to a glimpse at this alien world that anyone can enjoy.

So next time you're walking past a stream, stop to take a closer look. Or head over right now to http://www.troutnut.com. Either way, you'll be amazed.