Four short lines, and the whole poem is a single image: the ocean as a kind of drink, a vast liquid that swallows what we throw away. The title, "Gyre," points to the huge circling currents in the sea where floating debris collects. So the "spoils of our joy" are the leftovers of everything we enjoy, the plastic, packaging and waste of a consumer life, all drifting together in a slow, enormous turn.
The speaker's tone is quiet and unsettled. Calling the ocean "the drink" sounds casual, almost like a toast, which makes the picture more uncomfortable. The word "spoils" works two ways: it suggests treasure taken in victory, but also things that have rotted. The last line, "one burial," is the sharpest. All our separate pleasures end up in one shared grave. The mood is somber and a little accusing, yet the poem never shouts. It simply lets the image sit there and turn.