dà hǎi lāo zhēn
lit. to fish a needle from the sea
to find a needle in a haystack (idiom)
shí tóu dà hǎi
to disappear like a stone dropped into the sea
to vanish forever without trace
shí chén dà hǎi
lit. to throw a stone and see it sink without trace in the sea (idiom)
fig. to elicit no response
pàng dà hǎi
malva nut
seed of Sterculia lychnophora