(like) water off a duck's back
Meaning: You can say an insult or criticism is like water off a duck's back if it doesn't upset you.
- I asked Amy if she got upset when journalists wrote negative things about her, and she said she didn't care what they wrote - it was like water off a duck's back.
- Terry said he was too sensitive about criticism and he wanted to be like one of those people for whom it's like water off a duck's back.
Many people claim that insults or negative comments are like water off a duck's back, but in reality, many of them are