noun
hidden gem; unrecognized talent
A yojijukugo (four-character idiom) of Chinese origin, meaning a talented person who remains unknown to the world, like a pearl lost in the vast sea. Rare and literary.
彼は滄海遺珠とも言うべき画家で、生前はほとんど評価されなかった。
He was a painter who could be called a hidden gem, hardly recognized during his lifetime.
この作品はまさに滄海の遺珠、埋もれさせるには惜しい才能だ。
This work is truly a pearl lost in the vast sea; it would be a shame to let such talent go unnoticed.
From Chinese cānghǎi yízhū (滄海遺珠), literally 'a pearl left behind in the vast sea'. The exact historical derivation is uncertain, but it is used as a metaphor for an undiscovered person of great worth.