The scene is important because it shows the two most significant lines of plot unfolding.Firstly, Antonio accepts Shylock's bond, one pound of flesh in return for three thousand ducats. Secondly, Shylock appears and reveals something about his personality to the audience. The author presents a compelling and controlling individual adding to the strong drama he will create later.
Shakespeare has arranged events so that a character has put his arrogance as collateral of a loan. Only Fate can decide which way it blows- how terrible to be at the mercy of something so unpreductable as the weather at sea! Shylock however relies on black and white facts only - you pay or you don't so it is simple for him. He is not interested in any grey areas of extenuating circumstances. The plot is developed with audience horror and fear as the suspense builds.