(like) water off a duck's back

US /ˈwɔtər ɔf ə dʌks bæk/
UK /ˈwɔtər ɔf ə dʌks bæk/
"(like) water off a duck's back" picture
1.

鴨の背に水, 全く効果がない

criticism or negative comments that have no effect on someone

:
He tried to insult her, but it was like water off a duck's back.
彼は彼女を侮辱しようとしたが、それは鴨の背に水だった。
Criticism rolls off him like water off a duck's back.
批判は彼にとって鴨の背に水だ。