expression, ichidan verb
still waters run deep
Proverb meaning that a quiet or calm exterior often hides depth, wisdom, or strong emotions.
彼はあまり話さないが、深い川は静かに流れるというから、きっと深い考えを持っているのだろう。
He doesn't talk much, but still waters run deep, so he probably has profound thoughts.
A similar proverb about hiding one's talents, but 深い川は静かに流れる focuses more on depth of character or emotion rather than ability.
A Japanese proverb equivalent to the English 'still waters run deep'. The exact origin is uncertain, but it likely entered Japanese through translation of Western proverbs or as a natural metaphor.