How is the first paragraph of the story important to the passage as a whole?

The first paragraph of the story goes a long way toward setting the mood for the text. There is something sad about the statement that none of the men "knew the color of the sky." It is as if there is nothing more in the world than what one can see before oneself, no chance of a higher power or redemption, second chances, or even purpose. The waves are the color of "slate," a dark and oppressive gray; this color feels impenetrable and heavy, like the stone for which it is named. Further, the narrator says that

The horizon narrowed and widened, and dipped and rose, and at all times its edge was jagged with waves that seemed thrust up in points like rocks.

This description of the horizon changing uncontrollably and unpredictably contributes to the idea that life is both uncontrollable and unpredictable. Further, the negative connotation of a word like "jagged" and the description of the water that looks like pointed and dangerous rocks, adds to the unknowability of a world where water can seem like sharp stone. The mood is heavy and menacing, as though there is always some danger awaiting on the horizon, a horizon that is ever-changing.