The elongated letter "S" is Hogarth's Curve of Beauty and Grace, also caused the S-Curve, much used in fashion photography and graphic design for advertisements.  The letter "W" has two overlapping Hogarth curves.

More and better Hogarth's curves may be found on mountain ridges in Landscapes and Natural Landscapes.  The canoe landscape below is an example.  Next, the rappelling scout forms the curve.  A reflection in the water will double the number of curves.

Explanation of the S-Curve (after clicking, scroll down the page) in Geometry in Composition and Guidelines for Better Photos.

See also how expert photgraphers portray Hogarth's Curve 1 and Hogarth's Curve 2.
.
.

.

Boy Scout Troop 174, Yorktown, NY.  Scouting Photography Pages at  http://troop174.info