水中捞月的英文：
[Literal Meaning]
water/inside/pick up/moon
to pick up the moon in the lake

[解释]
到水中去捞月亮。比喻去做根本做不到的事情，只能白费力气。

[Explanation]
to make vain efforts

[例子]
你这么做等于是水中捞月，一点收获都不会有。

[Example]
What you did is to make vain efforts and you will gain nothing.

[英文等价词]
to fish in the air