This poem is written in free verse, which means that it has no set pattern of rhythm or rhyme. Yet, Plath uses rhythm and rhyme deliberately. While her lines have no repeating pattern of stressed and unstressed syllables, they read gracefully and naturally.
While none of these lines rhymes blatantly, Plath uses slant rhymes, or words that sound similar, but don't quite rhyme. An example of this is the lines ending in "darkness" and "fish" – these two words sound similar, but the slant makes the rhyme surprising and fresh. Plath also uses repetitive phrases, like "over and over" and "day after day." These phrases, and Plath's attention to sound, help bring a little rhythm and rhyme into this poem's free verse.