Formal or literary term

the blue sea; blue waters

blue waves; blue wave

hair that has lost its shine due to ageing

Rare term; Formal or literary term

great blue sea; ocean

From a Chinese legend

the world is a scene of constant changes (as a mulberry field changing into a blue sea)

the world is a scene of constant changes; the blue sea turns into a mulberry field

Rare term

talented person unbeknownst to the world

Idiomatic expression

drop in the bucket; drop in the ocean; one grain of millet in a vast ocean

Proverb

the world is a scene of constant changes; a mulberry field changes into a blue sea