Rapids are a place of extremes -- extremes in water depth, extremes in bottom erosion, extremes in even current speeds, as we shall see. Rapids are always better places to be searched carefully by the fly fisher -- carefully in terms of wading, and carefully in terms of making certain that no good water goes unexplored.

Rapids are tough places to put a fly down and expect it to float with any sort of dead drift. But there are some tricks to it. First comes reading waters, then comes the fishing. In all rapids, there is a "secret river". It may be quite narrow, and then again it may be fairly wide. It's the easy water, the place one can toss a fly without much need to do more than use a Harvey-style leader to get a good float. During the salmon fly hatch [on Montana's Madison River] (and every other hatch for that matter), the fishing can be fast and furious in the secret river, and it's the first place I hit. It's the water right against the bank -- you know, that stuff one wades through to get out there into the "real" river. But think about it for a moment: Where's the best place for an energy-conserving trout to park itself while getting food in the easiest fashion? That's right: In the slow water next to the shore where the stoneflies are hanging on every bush like overly ripe fruit.

When guiding anglers on the Madison, my long-time friend, Mike Lawson, tells clients to cast into all those places where one wouldn't normally fish -- in other words, the secret river. Those that pay attention to his advice find out very quickly that Mike is a shrewd water-reader, indeed. Most anglers use the secret river as their wading lane, when in fact, it should be their fishing lane.

So, lesson number in in reading rapids is very simple -- find the secret river on either side of the rapids, and fish it hard. Some of it will be deep and some of it will be shallow, so expect to find a mixture of prime lies and feeding lies. Some of it may have undercut banks and sometimes there are boulders blocking your wading; too deep on the outside to go around and too tall to clamber over. One has to haul out and walk around. But when you do, watch it. The hydraulic cushion right in front of that boulder may be holding a boulder-sized brown. Don't race through the secret river.

A not-so-secret secret river (red dots) on the Yellowstone, inside Yellowstone National Park (photo: Chad Shmukler).

Interestingly, the secret river is not a secret at all to one select group of individuals. In fact, it is their preferred area to fish. This set of individuals are the float guides. Their mantra, repeated time and time again to clients who struggle to comply, is: "Get the fly closer to the bank."

Odd, isn't it? The guys floating mid-river are told by their guides to pound the banks, while the guys that are wading struggle to get their flies to mid-river.

Editor's Note: The above is an excerpt from "Reading Waters", by Gary Borger. It is the second book in Gary's "Fly Fishing: The Book Series". As we've noted before, if you're not familiar with the series, you're missing out. Each book is a fountain of information resulting from years of well-heeled experience. The first three books offer a bevy of knowledge. Most importantly, the lessons in the book are illustrated by warm, entertaining anecdotes from Gary Borger's life as a fisherman, making the books not only valuable tools for the fly fisherman, but an absolute pleasure to read. To learn more about the entire series, visit GaryBorger.com.