"Thetis" bursts with alliteration, which, alongside assonance and consonance, fills the poem with rich music that brings its story to life. For example, in stanza 1, the alliterative sibilance mimics the gentle, soft quality of Thetis's song:
Sweet, sweet, was the small song
that I sang,
There's more sibilance in lines 13 and 14, though here the device produces a somewhat different effect:
So I shopped for a suitable shape
Size 8. Snake.
Alliterative /s/ and /sh/ sounds cast a sinister hush over the poem and evoke the hiss of a snake—not coincidentally, the form that Thetis takes here. Similarly, the /s/ alliteration of lines 25-26 mirrors the fluidity of a fish moving through water:
I sank through the floor of the earth
to swim in the sea.
Elsewhere in the poem, harsher consonant sounds create a more violent tone. This type of alliteration typically appears in sections describing Peleus's actions. Take, for example, line 12, in which Thetis's wings are "clipped by the squint of a crossbow's eye." Here, the repetition of a sharp /c/ mimics the bite of an arrow. Similarly, lines 23-24 contain repeated hard /g/ sounds:
But my gold eye saw
the guy in the grass with the gun. Twelve bore.
This harsh, guttural repetition pierces the sound of the poem much like a gunshot pierces the air.