The poem never says the word "water," but the title, "Aqueous Facts," gives the answer away. Each couplet circles one idea: water is in us, and it links everything else too. The speaker starts close to home, noting that their own body is made from it and that it makes every part fit together. From there the view widens. Water carries "ancient information," as if it holds a memory far older than any person, and it is "independent and free in his creation," a force that answers to no one.
The middle and end push the idea outward. Water joins the hobo and the king, so it ignores rank, and it crosses every border and distance, so it ignores geography. The speaker calls it a "universal law."
The mood is calm, awed and quietly reverent, like someone stating a simple truth they find amazing. The short, rhymed lines (fit/it, king/everything) give it a steady, almost chant-like feel, as though the speaker is listing facts they trust completely.