to look for a needle in a bundle of hay
海底捞针 to look for a needle in a bundle of hay 差之毫厘失之千里 A miss is as good as a mile ..
海底捞针,汉语成语,拼音是hǎi dǐ lāo zhēn,意思是在大海里捞一根针,形容很难找到。出自《二郎收猪八戒》。