Still waters run deep

Cultural  

1. A person's calm exterior often conceals great depths of character, just as the deepest streams can have the smoothest surfaces.

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still waters run deep Idioms  

1. A quiet person may be very profound, as in Susie rarely says much, but still waters run deep. The physical observation in this term dates from ancient times, but it has been used figuratively since about 1400. Anthony Trollope amplified it in He Knew He Was Right (1869): “That's what I call still water. She runs deep enough. . . . So quiet, but so—clever.”

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Example Sentences

The filmmakers — Janus Metz directed, from a screenplay by Ronnie Sandahl — focus on the melancholy Swede, perhaps out of Scandinavian pride and perhaps because they believe his still waters run deep.

From New York Times • Apr. 11, 2018

In Lightfoot’s songcraft, still waters run deep, or at least deeper than you’d expect for someone who became branded an easy-listening artist.

From Washington Post • Nov. 2, 2017

My, but Tom Jacobson’s still waters run deep.

From Los Angeles Times • Sep. 20, 2017

She is one of those characters, of whom it has been said proverbially, that "still waters run deep."

From Characteristics of Women Moral, Poetical, and Historical by Jameson, Mrs. (Anna)

"Sometimes still waters run deep," said Miss Hilary.

From Mistress and Maid by Craik, Dinah Maria Mulock