沧海

cāng hǎi yī sù

沧海一粟

a drop in the ocean

cāng hǎi yī shēng xiào

沧海一声笑

see the world indifferently

céng jīng cāng hǎi nán wéi shuǐ

曾经沧海难为水。

One who has seen the ocean thinks nothing of mere rivers.