In Chapter Four Nick learns about Gatsby's past as he "sprang from his Platonic conception of himself" and his fancies began after meeting Dan Cody whose yacht dropped anchor in Lake Superior where he was a poor young man working as a clam digger and salmon fisher.
To young Gatz, resting on his oars and looking up at the railed deck, that yacht represented all the beauty and glamor in the world.
It was then that Jay Gatsby moved into the life of the wealthy as he became a sort of personal aide to the alcoholic Cody as a steward, secretary, skipper, and even "jailor." Gatsby did this for five years until Cody "inhospitably died." He left Jay $25,000, but Cody's mistress took it. But, from then on the "vague contour" of Jay Gatsby began to develop, for his desire for the things that only money could buy grew in his heart, and he pursued his materialistic goal from then on.
In F. Scott Fitzgerald's classic of American literature, The Great Gatsby, the titular character is escorting Daisy Buchanan and Nick Carraway, the story's narrator, through his mansion (an ostentatious display of nouveau-riche excess) when they come to a photograph of a yacht hanging on the wall above Gatsby's desk. As Nick describes the scene,
"I began to walk about the room, examining various indefinite objects in the half darkness. A large photograph of an elderly man in yachting costume attracted me, hung on the wall over his desk. ‘Who’s this?’ ‘That? That’s Mr. Dan Cody, old sport.’ The name sounded faintly familiar. ‘He’s dead now. He used to be my best friend years ago.’ There was a small picture of Gatsby, also in yachting costume, on the bureau—Gatsby with his head thrown back defiantly—taken apparently when he was about eighteen."
A young, lost James Gatz is entranced by the image of the yacht he observes, the property of a silver mining magnate named Dan Cody, whose wealth and prestige become the immediate model to which the teenager aspires. The yacht symbolizes wealth and social status. James Gatz will, of course, invent a new identity for himself as Jay Gatsby, and his relentless pursuit of the life represented in that photograph of Cody's yacht, as well as his obsession with Daisy, will prove his ultimate undoing.