What I get most from this section is that the woman who observes the young men is the quintessential poet, simultaneously outside of the scene (how else is she to observe it?) yet more inside the scene than any of the actual participants.
Too, I go for the tremendous appeal Whitman makes to the senses, without which no poem can triumph—when, in her imagination, she joins the bathers two stanzas later, Whitman continues, “An unseen hand also passed over their bodies, / It descended tremblingly from their temples and ribs.”
Finally, I love the generosity of the number twenty-eight. Much has been made of that figure, that it represents the number of states in the union when Whitman began writing or the lunar or menstrual cycle or some aspect of Egyptian mythology.
But Whitman rivals Shakespeare in his desire to give the reader more words, more images, more lushness. I say he just wanted a lot of bathers.