This is not the equivalent of the English idiom: “a big fish in the little pond.” Instead, learn to use this idiom to talk about people with shallow knowledge.
井底之蛙(Jǐng dǐ zhī wā): a frog in the well
The frog at the bottom of the well can only see a piece of sky as big as the mouth of the well. Therefore, it is used as a ridicule of people who have little knowledge and no vision. Nowadays, netizens often use this word to attack others who are not in the same echo chamber to show superiority.
Example:
你們這群井底之蛙到底懂什麼呢?
Nǐmen zhè qún jǐngdǐzhīwā dàodǐ dǒng shénme ne?
What the hell do the frogs in the well like you understand?
