" In high water, fish migrate to the banks to stay out of the fast currents and to take advantage of the worms, beetles, ants, and other terrestrials being swept into the river by the floodwaters. If the water is very dirty, they position themselves right next to the bank, a rock, or the bottom in order to keep their equilibrium. In warm water, they move to the deeper cooler waters or place themselves near a cool spring or tributary. Alternately, they could be under the fastest turbulent cascades where there is more dissolved oxygen. "

― Yvon Chouinard , Simple Fly Fishing: Techniques for Tenkara and Rod and Reel