The poem begins with a description of the River Thames where Spenser finds two beautiful maidens.
The poem begins with a fine description of the day when on which he is writing the poem: Calm was the day and through the trembling airThe sweet breathing Zephyrus did softly play.The poet is standing near the Thames River and finds a group of nymphs with baskets collecting flowers for the new brides.
According to the myth, Jove falls in love with Leda and comes to court her in the guise of a beautiful swan.
American-born British poet T. S. Eliot quotes the line "Sweet Thames, run softly, till I end my song" in his 1922 poem The Waste Land.
English composer George Dyson (1883–1964) set words from Prothalamion to music in his 1954 cantata Sweet Thames Run Softly.