The Father's knowledge of sailing vocabulary suggests he is familiar with the sea and sailing. This is bolstered by the Father's insistence that he and the boy continue on their journey to the coast. In the post-apocalyptic world, it seems human nature to gravitate toward the familiar. Since the Father wants to go to the coast and is able to tell the Boy about the blue sea, he is familiar with it.
There is more going on than just the suggestion of familiarity with sailing though. The story is about the dramatic change in life between what the Father knew and what the Boy knows now. The sailing terms are a constant reminder of this disparity. It also offers a deeper sense of the Father without a clear defined past. By alluding to and describing the ocean, Father is trying to pass along the grandeur of the world he knew to the Boy. The vocabulary serves as a sad reminder that such terms will become archaic and represent an ideal past which is no longer possible.