In short, two lovers, the morning after, contemplate what they were before they met. I will focus on the use of anaphora in the section below, as well as the twelve syllable lines that end each stanza.
In anaphora, we expand outwards imagery-wise from sea-discoverers to maps to the new world/new worlds/ the world, while contracting inwardly metaphorically into the subjective reality each lover contains.
I can’t think of much to say without repeating myself, so I will focus on the odd 12 syllable line that ends each stanza. Why 12 syllables? It breaks the steady flow of iambic, and it’s so ungainly. Why? Well, to me, it suggests a determination on the part of the narrator to clarify what he is saying with each successive phrase. Also, it places greater emphasis on the end rhyme: thee, one, and die. Now, off to record it the best I can.
I hope this is a help to someone. As you can see from this commentary, I am not a lit major, nor will ever be, but I enjoy engaging with poetry and learning from it. Thanks for reading.