There is a lotus, a child and a fish in the picture. What is an idiom?

Yue longmen, a carp ―― Climbing the social ladder.

[Pronunciation]

[Explanation] It is said in ancient times that the Yellow River carp will turn into a dragon when it jumps over the Longmen. Metaphor promotion, promotion and the like. It is also a metaphor for going upstream and striving for progress.

[Source] Yaya Shi Yu: "As the saying goes, a fish jumps over the Longmen, but only carp is possible."