Previously on this blog, I’d reflected upon (and praised!) Peter Sack’s notion of the “dolphin’s turn.” As I noted in that post:
According to Sacks, the dolphin’s turn is “a transformative veering from one course to another, a way of being drawn off track to an unexpected destination…” (Sacks adds: “[T]his turn is paradigmatic for the transportation system of poetry itself, both in its technical “versing,” and in its thematic and figural changes.”) The dolphin is associated with such turning, of course, because it is a creature that itself is always transgressing boundaries, leaping and diving.
In large part, Sacks’s lecture (which you can listen to here) is an analysis of the dolphin’s turn as it occurs in a variety of poetic works, from the “Homeric Hymn to Pythian Apollo” to poems by Mandelstam, Celan, Bishop, and others.
One poem Sacks did not mention, but which I think deserves mention, is John Keats’s verse epistle to his brother George, and I make my case for my view over at the Keats Letters Project. (You can link directly to it here.)
While you should read Sacks, and perhaps my extension of his thinking, Keats’s verse epistle is required reading for those who love poetic turns. Dive in!
Structure & Surprise 
I am an amateur poet and English teacher in Tampa, and I have enjoyed visiting this blog periodically for several years and have often used the turn in my teaching.
This subject of the dolphin’s turn is particularly fascinating to me, and I adore Keats’s work. One of my favorite turns of all time is in “This Living Hand,” where the imagery of his hand turns from living, to dead and rotting, and back to living.
Thank you for your excellent work here. I may try to employ the dolphin’s turn in my next project, and I will certainly continue to spread the gospel of the turn.
-Aaron
Apologies for my (very!) late reply, Aaron– Thank you for these very kind words–they mean a lot! Keep me posted if you do more work with the dolphin’s turn (or any others). I’ll try to do better at being more timely. Cheers to you, Aaron!