The Mysterious Deep is a ribald poetic form intended to express pleasure with mist, originating in The Fortunate Confederacy. The rules of the form are applied by poets to produce individual poems which can be recited. The poem is a series of quatrains. Use of elision is characteristic of the form. Forms of parallelism are common throughout the poem, in that certain lines often share an underlying meaning and they are required to maintain phrasing. The rhyme scheme of the poem is AAAB.