Fishing for the moon in water is a legendary fable. It's about a group of monkeys hanging on a tree, one by one, going to the water to catch the moon, only to find that the moon is hanging in the sky. This is a text in primary school.

Later, it was also compared to doing something that could not be done at all, and it could only be in vain.

"Fishing for the Moon in Water" originated from a fable of Buddhism. According to the law of monks, Buddhists and monks said that 500 macaques used to play in the forest and came to a well. The macaque thought there was a moon (shadow) in the well, so he said to his companions: The moon died today and fell into the well, so we should fish it out. Exhibition and rotation are connected, and it is possible to come out. So all the monkeys fell into each other's exhibition, the trees were weak and the monkeys fell into the well water. The Buddha used this story as a metaphor for those heterodox teachers who are self-righteous, can't tell right from wrong, and harm others and themselves.