Meaning of the word "(like) water off a duck's back" in English

What does "(like) water off a duck's back" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

(like) water off a duck's back

US /ˈwɔtər ɔf ə dʌks bæk/
UK /ˈwɔtər ɒf ə dʌks bæk/
"(like) water off a duck's back" picture

Idiom

criticism or negative comments that have no effect on someone

Example:
He tried to insult her, but it was like water off a duck's back.
Criticism rolls off him like water off a duck's back.