Male Waters Run Deep
We have defective mythologies that ignore masculine depth of emotion...
Robert Bly - Iron John
And yes I do mean affect.
Most often I hear "still waters run deep" said to imply quiet people have the deepest character. Generally it is employed defensively to evoke sympathy for a family member or friend or to deflect attention from their deficits, negative manners or anti-social behavior. Now it may be true that quiet people often have the deepest character, but a majority of the time that character is deeply broken or mired in the sewage of base and immoral values.
Though now commonly used to assert that a placid exterior hides a passionate or subtle nature, historically the more negative reality prevails. As the following fable demonstrates, formerly “still waters run deep” carried a warning that silent people are dangerous.
A farmer was about to cross a rushing stream which by chance had swollen with rains, and he sought a ford. First, he tried that part of the stream which seemed quieter and more peaceful, and he found it to be deeper than he had thought. Then he found that place was shallower and safer where the stream flowed by with a greater burbling of the waters. Then he said to himself, "How much more safely can we entrust our life to the roaring waters rather than to the quiet and noiseless waters." We are warned by this fable that there is more danger in the reserved and silent person than in a noisy, babbling enemy.
This warning reflects the nature of a deep quiet river. Contrasting a quiet river with a small brook helps clarify the meaning. A small brook often sounds and looks noisy and bubbly and shallow. The noise and the roughness are in proportion to the size, frequency and shape of the rocks and debris in the water. The quieter and smoother the brook, the smoother the bottom of the stream.
Now look at the Yellowstone River. The places where the surface remains placid often hide the most danger.
A string of railroad box cars once fell into one such stretch of the river. The current under that placid top was so strong it carried them immediately down and out of site. In fact a search for them revealed that the bottom could not be reached. Between the depth of the water and the violent undercurrents not a trace of the string of box cars has ever been found.