Windshield of Trees
While Lewis is driving Ed into the woods towards the river the camera stays on the windshield and peers through at the two men. We see the reflection of the sun and the trees rolling over the top of the men as they drive deeper towards the river. The image shows us that they are being overtake by nature, by the woods that they don't know. And the faster they drive the more we understand that they don't know what they are getting themselves into.
One Man in Between
While the men are deciding what to do with the body of the man that Lewis has just killed. We see Lewis looking at Bobby in a clear line and then Lewis looks Ed and this time Drew stands between the men. The image shows that Ed is the man that can be reasoned with to do the right thing as Drew speaks to him. But we also see that he is the key to burying the man. If he agrees then the men do it, if he doesn't then they go to the police and this image builds the tension of the moment to a higher degree.
The Dig
As the four men dig into the earth in order to bury the man that Lewis has killed. We see Lewis, Ed and Bobby dig at an even pace while Drew digs feverishly. The imagery shows how upset Drew is with having to do this and that he is separated from the others. It also shows his desire to get this horror over with as soon as possible.
Into the Rapids
After Lewis kills the man, the men head into the river and believe they are home-free if they can just make it to the end of the river. We then see them plunge into the rapids where Drew falls out and loses his life and Lewis breaks his leg. The image of the rapids is a literal expression of the way these men are feeling. Completely turned up inside to the point that they are ready to be thrown out of there own skin just like they are from their canoes.
