Somewhere in your favorite stretch of a river there’s a depression at the bottom. It’s wide enough and long enough to hold a trout, nose to tail. It’s as deep as the trout is tall — or a bit deeper. The river flowing over this depression in the riverbed is fast enough to bring a continuing buffet of food. And the water comes with the right shade, ripple or depth to offer good protection. This is a special bucket. Let’s break it down . . .