The word "shi" should be pronounced as the first sound, which means that a feather looks wet. This sentence describes that a fish's tail is like a wet feather. In China's ancient poems, fishing is often used as a metaphor for courtship between men and women. This is the answer in the textbook of ancient Chinese poetry, edited by Zhu Dongrun, which is quite authoritative.
What is the meaning of "He" in "How the bamboo pole curls" and why the bamboo pole swings with the wind; "A fish's tail is nothing but a disciple" is why the fish's tail is like a wet feather. Metaphorical courtship between men and women.