There are dozens of holes like this about 4 miles downstream from the bridge near Chitina on the Copper River. They are all down in the canyon where the water current forms big, slow eddies where the fish can rest out of the main current.
+davao0506 The fish are relaxing in the eddie, out of the current. They are so accustomed to using full power in their trip up the river that they forget that it doesn't take very much energy to stay in this slack water and so sometimes they swim too hard and breach.
