懂中文 Dong Chinese

大海撈針

dà​hǎi​lāo​zhēn

lit. to fish a needle from the sea

Definitions

大海捞针 (大海撈針) 

dà​hǎi​lāo​zhēn

lit. to fish a needle from the sea; to find a needle in a haystack (idiom)

Sources