The effect which the repeated "s” sound have on this part of the poem is;
The addition of rhythm to the poem. It also adds a sneaky mood to the poem.
The repeated use of the 's' sound in this poem is reflective of a poetic device known as alliteration.
Alliteration is the repetition of the initial sounds of consonants in a group of nearby words.
Alliteration is an important poetic device because it helps to add rhythm to a poem.
In the poem, we see an individual being described who got something easily. Just like the crawling of a snake, the 's' sound used in this poem also adds a sneaky feeling/mood to it.