"Swiftly, swiftly flew the ship,
Yet she sailed softly too:
Sweetly, sweetly blew the breeze—
On me alone it blew...."See in text(The Rime of the Ancient Mariner in Seven Parts)
These mirroring, rhyming phrases of “swiftly, swiftly flew” and “sweetly, sweetly blew” also contain two paradoxes. The ship flies “swiftly” but also “softly,” which is difficult for any vessel to do when travelling across an entire ocean. Furthermore, the wind blows on the Mariner but on nothing else around him, underscoring the sheer impossibility of this event.
"The fair breeze blew, the white foam flew,
The furrow followed free:..."See in text(The Rime of the Ancient Mariner in Seven Parts)
Coleridge uses a lot of words that start with the letter f in this stanza for expressive purposes. Repeating letters at the start of words is called alliteration. Try reading this passage out loud. All of those f-sounds imitate the sound of a blowing wind.