It means that the water is too clear for fish to survive; Metaphor should be tolerant and casual, not too harsh;

From Bangu's Hanshu Volume 65 and Biography of Dong Fangshuo Volume 35;

The whole sentence "Poetry" says:' How can we sympathize with other people's words if the etiquette and righteousness are not satisfactory? Therefore, there is no fish in clear water, and there is no disciple in human observation. Crown in front, so cover it; I am deaf, so I am busy. "

Explain the Book of Songs and say: There is no need to care about people's comments if there is no propriety and righteousness. Therefore, there is no fish when the water is clear, and there is no disciple when people look at it. There are jade ornaments in front of the crown, which are used to block the line of sight, plug the ears with silk wool and weaken the hearing.