How does John Casey use imagery in Spartina?

Imagery:

"There's a knack to how you look. You got to . . . unfocus your eyes. What you want to do is let as much come in as you can. You don't so much see a fish as you just get a feeling that something's different. You just feel a speck on your screen. Then you focus in. Most of the time it's a shadow of a wave, or seaweed or flotsam. You'd be surprised how much junk is out here."

"There's more, but that's the pattern. You spend a lot of time dividing up the world into the idle rich and the true-blue salts. The unworthy and the worthy. And what do you get out of all this? You get to feel pissed off. Am I leaving something out? You get to feel salty as hell, but mainly pissed off. You also get to feel poor. Tonging quahogs in your eighteen-foot skiff."