What is the meaning of "like a fish turning into a dragon"?

It is a kind of dragon head fish body of the dragon, but also a kind of "dragons and fish change each other" form, this form of China's ancient times, for the generations of folklore, legend derivation, its long history, can be traced back to the prehistoric Yangshao culture - half-slope type of period of the fish totem worship, the "Great Wilderness Western Scripture" has "Wind Road north, the sky is a big water spring, the snake is transformed into a fish." It is an early transitional form of fish changing into dragon. The dragon is the deified snake and worm, "Overseas South Scripture" cloud: "Worm for the snake, snake number for fish." Folk customs have long been associated with the transformation of fish into dragons. Confucius Family Tales" records: Confucius was happy to get a noble son, Lu Zhao Gong to carp as a reward, Confucius therefore named his son carp, the word Bo Yu. Said the court" in the "white dragon in the past under the clear cold abyss into a fish" record, "Chang'an ballad" said the "East China Sea fish into a dragon" and folk legend of the carp jumped over the Dragon Gate, are about the relationship between the dragon and the fish mutation. This kind of modeling appeared in jade carving as early as the late Shang Dynasty, and has been developed through the ages. Traditional Allegorical Patterns. Also known as "Fish and Dragon Change". The transformation of a fish into a dragon is an ancient metaphor for getting a title in the Golden Ranking. Feng's Wenshimianji, Volume 2: "Therefore, in contemporary times, the entrance to the imperial examination is called the Dragon Gate." Li Bai (李白《与韩荆州书》)："Once you reach the Dragon Gate, your reputation is multiplied a hundredfold." Pipa Ji (The Story of the Pipa): "My child is going out today, and my father and mother have come to see me off, but I wish to be transformed into a dragon and rise to the top of the green clouds." Patterns are generally composed of fish and dragons, implying high prosperity.