[deep blue sea;the sea] 大海。以其一望无际、水深呈青苍色,故名 东临碣石,以观沧海。--《乐府诗集·曹操·步出夏门行》
沧海桑田cānghǎi-sāngtián
[the swift changes of the world;great changes are seen in the course of time;the evanescence of the worldly affairs is like the sea turned into a mulberry field (orchid)] 大海变成了种桑树的田地,种桑树的田地变成了大海。比喻世事多变,人生无常;或喻世事变化的巨大迅速--略称沧桑 山河改转,沧海桑田