Teach fish how to swim is an idiomatic expression derived from the Latin proverb . The phrase describes the self-sufficiency of those who know better how to do everything than the experts. It corresponds to the expression, " teaching grandmother to suck eggs".

Erasmus Desiderius Erasmus Roterodamus (; ; English: Erasmus of Rotterdam or Erasmus;''Erasmus'' was his baptismal name, given after St. Erasmus of Formiae. ''Desiderius'' was an adopted additional name, which he used from 1496. The ''Roterodamus'' w ...

attributed the origins of the phrase in his ''

Adagia ''Adagia'' (singular ''adagium'') is the title of an annotated collection of Greek and Latin proverbs, compiled during the Renaissance by Dutch humanist Desiderius Erasmus Roterodamus. Erasmus' collection of proverbs is "one of the most monum ...

'' to

Diogenianus Diogenianus ( el, Διογενειανός, Διογενιανός) was a Greek grammarian from Heraclea in Pontus (or in Caria) who flourished during the reign of Hadrian. He was the author of an alphabetical lexicon, chiefly of poetical words, ...

. A corollary idiomatic phrase is part of common usage in Chinese ""Muehl, Louis Baker ''et al.'' (1999).
班门弄斧
display one's slight skill before an expert e.g. 在你面前班门弄斧,太不好意思了 (I'm making a fool of myself trying to show off before an expert like you)

References

{{reflist English phrases