The Perch of Sponge-people is a ribald poetic form intended to teach a moral lesson concerning rivers, originating in The Harp-Seal of Shying. The form guides poets during improvised performances. The poem is two to four quintains. Use of simile is characteristic of the form. Forms of parallelism are common throughout the poem, in that certain lines have similar grammatical structures, they use the same placement of allusions and they reverse grammatical structures. Each line has four feet with a syllable weight pattern of long-short-short (quantitative dactylic tetrameter). The rhyme scheme of the poem is AABAA.