The water that looks calm on the surface is usually of great depth, and the water that even a gentle wind can ruffle is shallow.
Still waters run deep , goes the proverb.
This is true even of human nature. We cannot judge people by their gentle and humble appearances. For all you know, they might possess some extraordinary and exceptional talent. Just like the calm water at the surface of the deep sea, the depth of which, cannot be judged.
Thus, a learned person may not show off his or her knowledge. His or her unassuming nature could make you say, “Still waters run deep!”
The proverb can be used in another context too. A person who has lost a dear one may appear unaffected; but the calmness may be hiding the extreme anguish that he or she might be going through. “Still waters run deep!”
