What does nick say Gatsby is watching over?

Nick says that Gatsby's act of standing on the dock staring off is like he is "watching over nothing." In fact, Gatsby is gazing in the lighted direction of the object of his affection, Daisy, the woman who has been so idealized in Gatsby's head that the reality of her persona cannot possibly compete with the preconceived notions that Gatsby had developed. She is represented as beautiful and charming, but in the end Gatsby's expectations were still let down. The mental picture of Daisy meant everything to Gatsby, but the real Daisy meant nothing.