still waters run deep

Alternative forms

 * still water runs deep

Etymology
Of Latin origin, but possibly popularized by, c. 1590, in "Henry VI," part 2, act 3, scene 1:
 * Smooth runs the water where the brook is deep;
 * And in his simple show he harbours treason.

Proverb

 * 1) A person with a calm appearance has, or may have, considerable inner emotion, character, or intellect.

Translations

 * Arabic:
 * Moroccan Arabic: دوز على لواد لهرهوري ولا تدوز على لواد سّكوتي
 * Bashkir: йыуаштан йыуан сыға
 * Belarusian: у ціхім балоце чэрці вядуцца
 * Bulgarian: ти́хите води́ са на́й-дълбо́ки
 * Chinese:
 * Mandarin:
 * Czech:
 * Danish: det stille vand har den dybe grund
 * Dutch: stille wateren hebben diepe gronden
 * Finnish: syvissä vesissä ne isot kalat uivat
 * French:
 * German: ,
 * Greek: τα σιγανά ποταμάκια να φοβάσαι
 * Hungarian:
 * Indonesian:
 * Italian: l'acqua cheta rompe i ponti
 * Japanese:
 * Malay: diam-diam ubi berisi, diam-diam besi berkarat
 * Norwegian: det stille vann har den dype grunn
 * Polish:
 * Russian:, тихая вода́ берега подмывает
 * Serbo-Croatian: tiha voda brijege dere, тиха вода брег рони
 * Spanish: las aguas quietas calan hondo
 * Swedish: i de lugnaste vattnen går de största fiskarna
 * Thai:
 * Ukrainian: тиха вода греблю рве
 * Walloon: c'est todi l'aiwe ki doime ki neye, i s'fåt dmefiyî des coetès aiwes, i n'a rén d'pé ki l'coete aiwe