大海撈針

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

see 大夫[dai4 fu5]

big; large; great / older (than another person) / eldest (as in 大姐[da4 jie3]) / greatly; freely; fully / (dialect) father / (dialect) uncle (father's brother)

sea / ocean

surname Hai

ocean / sea / CL:個|个[ge4],片[pian4] / great number of people or things / (dialect) numerous

to fish up / to dredge up

needle / pin / injection / stitch / CL:根[gen1],支[zhi1]