The dragon swims in shallow water means the dragon is in shallow water.
The full sentence of this word is "A dragon swims in shallow water and is teased by shrimps; a tiger falls on Pingyang and is bullied by dogs", which comes from "Zengguang Xianwen". "Zengguang Xianwen" is a children's enlightenment bibliography compiled during the Ming Dynasty. The author has never found any book records. We only know that the Confucian scholar Zhou Xitao revised it during the Tongzhi period of the Qing Dynasty.
"A dragon swims in shallow water and is teased by shrimps, and a tiger falls into plain water and is bullied by dogs." The literal translation means: a dragon dares to tease even small shrimps in shallow water, but a tiger falls into plain water and is bullied by domestic dogs; free translation means: It is: A person who was originally powerful can be bullied by some small people once he loses power, lamenting that life is unpredictable.
Extended information:
January 19, 2015, 14:11, source: "Emperor Jin Min was taken captive to Pingyang by the Huns and killed after being insulted by Liu Cong" from Shenzhen Special Economic Zone Newspaper .
"Zeng Guang Shi Xian Wen" contains many familiar aphorisms, such as "A dragon swims in shallow water and is tricked by shrimps, and a tiger falls flat and is bullied by dogs." These two sentences describe the plight of those who have lost power. Easy to understand.
But the word "pingyang" is generally interpreted as a flat and bright place, which seems far-fetched, and it is not used in this way now.
I think Pingyang should be a specific place name. Ancient books have the so-called "Pingyang, the capital of Yao". Yaodu is now a district in Linfen, Shanxi, which is ancient Pingyang. It was discovered by Xiangfen archeology in 1978 The ruins of the Taosi Temple were unearthed, and some pottery fragments with written symbols were unearthed. Pingyang in the Han Dynasty produced great generals such as Wei Qing and Huo Qubing. The connection between "Tiger Falling on Pingyang" and it, I understand, is related to the Xiongnu, one of the Five Hus in the late Western Jin Dynasty.
Baidu Encyclopedia-Longyou was tricked by shrimps in shallow water
China News Network-Emperor Jin Min was taken captive by the Huns to Pingyang and killed after being insulted by Liu Cong