What is it when an author uses a concrete object to represent an idea

your answer is symbolism.

"the sandy walls seemed to collapse in on themselves"

and

"the bloodshot waters seemed to have no bottom"

hello! : )

i’m i haven’t read that. also you can’t really expect someone to write it for you. use your own knowledge and skill and i am sure you’ll get it!

good luck!

~ destiny ^_^