I can't tell my son what to do; it's water off a duck's back with him.

我无法告诉我儿子该做什么，他根本听不进去。

Let it roll like water off a duck's back.

让它像水开滚鸭子的背上。

Criticism falls off her like water off a duck's back.

批评对于她而言就像水流到了鸭子的背上，一滑而落。

The scolding ran off him like water off a duck's back.

那个家伙真是不可救药，我的一切警告他都当作耳边风。

Their hints about his behaviour were like water off a duck's back.

他们示意他举止不当，如同对牛弹琴。