I've chosen this paragraph from the chapter, "About the Ouse". It more than any other that I've perused over, captures the symbolic timless and cyclic nature that Swift attributes to this river in the particular, and all water in the general.
The Ouse flows on, unconcerned with ambition, whether local or national. It flows now in more than one channel, its water diverging, its strength divided, silt prone, flood-prone. Yet, it flows-oozes on, as every river must, to the sea. And, as we all know, the sun and wind suck up the water from the sea and disperse it on the land, perpetually refeeding the rivers. So that while the Ouse flows to the sea, it flows in reality, like all rivers, only back to itself, to its own source; and that impression that a river moves in only one way is an illusion. And it is also an illusion that what you throw (or push) into a river will be carried away, swallowed for ever, and never return. Because it will return. And that remark first put about, two and a half thousand years ago, by Heraclitus of Ephessus, that we cannot step twice into the same river, is not to be trusted. Because we are always stepping into the same river.