How does Chris Crutcher use imagery in Stotan!?

Imagery:

"We saw the notice about Stotan Week on the bulletin board just off the deep end of the pool after our early-morning workout today. It was already curling at the edges from the high humidity and chlorine content of the air, a lot the way my skin feels after a good three-hour workout."

"Somewhere in the couple of repeats I noticed things going soft at the edges; and we were a machine. Max put the bullhorn down and just called the starts. He didn't call out times or shout encouragement, or in any way risk jolting us out of the spell."