Misjudged

A rhino weighing just a ton, a baby still, in many ways, was thinking of a Marathon and planning a four-minute pace. But all the fat, so it would seem prevented any decent speed, that's why it swam, instead, downstream. It was more logical, indeed. And the gazelle, a jealous critter, quite capable to run full force was clearly skinny and much fitter, outpaced with ease the quickest horse. Gazelle saw rhino going fast and jumped into the raging stream. With spindly legs it powered past, but later learned it was a dream. A fatso weighing just a ton will win against a thin gazelle. The river was near Babylon, the tale is true. How could you tell?