this should help
Explanation: I decided to call to him. Miss Baker had mentioned him at dinner, and that would do for an introduction. But I didn't call to him, for he gave a sudden intimation that he was content to be alone—he stretched out his arms toward the dark water in a curious way, and, far as I was from him, I could have sworn he was trembling. Involuntarily I glanced seaward—and distinguished nothing except a single green light, minute and far away, that might have been the end of a dock. When I looked once more for Gatsby he had vanished, and I was alone again in the unquiet darkness. (1.152)
We never see Gatsby's version of America directly; we just get glimpses of it through Nick's narrative and through ephemera like his childhood notebook. But, judging from the way he's staring across the water, Gatsby has a pretty spectacular vision.