 CONT: When the Indians charge across the river toward the reverends  posse, the river changes both direction and color throughout the  scene. In some shots, the river is a muddy red, while in others it  is clearer and blue. In the shots of Ethan firing his rifle, the  river moves from his left to his right. But in the shots of the  Indians getting shot and falling from their horses, the river moves  from Ethans (and the viewers) right to his left. Then, as the  Indians retreat, the river switches back to moving left to right.