海中捞月

Explanation: Yu futile, waste of energy. 　　Source: "At first carved Pai An Jing Qi" Volume VII Lin'an government also can not do anything but to get the line clerical visit, the previous two bearers, but I do not know name, address, without a trace, the sea fishing month, saw a lady have to go somewhere else to send the. " 　　Examples: If you do not get this point clear, almost equivalent to ~ the same. ★ Guo, "Study of Ancient Chinese Society," Introduction to the Second Thesaurus:  not likely to happen in a century, once in a blue moon, walk with difficulty, fish for a needle in the ocean; look for a needle in a haystack, Impossible and, Makes all things easy, bark [bay] at the moon [bay the moon], the sound of footsteps in a deserted valley-a news or a statement which one does not hear often,or a thing that was seldom to found, Rarities, once in thousand years, sth.seldom seen or hardly possible as the iron tree blooms, Hard-won, defy Beyond the bounds of, strength of nine bulls and two tigers,mighty force, doomed petition like asking a tiger for its hide, Leather and Fox plan Antonym Group:  Have no choice but Shengji, Just to stoop and gather Are all, as thick as June blackerries, ubiquitous, overrun, cataclysm crosscurrent, Attracting attention Are all, common and numerous, Even flat-bed truck