水底捞针

Explanation: A needle under the water fishing. Described as difficult to find. 　　Source: Yuan Chang-ling, "Jiro close Pig," the third man off Jun children at home and look like needles, things in the days of temporary marriage, eliminate any chance points one reason or another? Delay directly to the present. " 　　Examples: Children off chance that the body is - I do not know what day the hand, how can people bear Pavilion girl. (Ming Feng Meng, "Awaken the common saying" Volume)