still waters run deep
Definition:  someone who may not talk or speak a lot may possess a lot of information about things
Usage:  if she were to open her mouth and talk, you will be surprised about the information she has - a typical example of still waters run deep

SEPEDI
Translation:  meetse ao a homotšego a iša fase
Proverb: meetselegakwa go išetša fase ke ga ona

XITSONGA
Translation:  mati mo tenga ma tsutsumela exidziveni
Proverb: nghala yi tumbeta vurhena

TSHIVENḒA
Translation:  maḓi o dzikaho o tsa vhukuma
Proverb: vhukale a vhu ḓiambi