Incorporating symbolism

"There isn't any symbolism. The sea is the sea. The old man is an old man. The boy is a boy and the fish is a fish. The shark are all sharks no better and no worse. All the symbolism that people say is shit. What goes beyond is what you see beyond when you know." --Ernest Hemingway (Of The Old Man and the Sea)

I'm querying a novel that contains tons of symbolism. Does your work contain symbolism? Do you know that a work will contain symbolism from the outset? Is it something you incorporate as you go? Do you go back and add the symbolism when you're done? Or do you even think of this as you're writing? And, lastly, what do you think of Hemingway's quote?