"Shadow" is a common light phenomenon in our daily life, such as "photography" during spring outing; "Shadow Play" of folk shadow play; The scenery on the shore is formed in the water.

A, photography is the use of convex lens to reverse image, restore, true, and the lens is the refraction principle of light, so A is wrong;

B, shadow play is the linear propagation of light, so B is wrong;

C. reflection is imaged by a flat mirror, and a calm water surface is equivalent to a flat mirror. The image formed by the plane mirror is symmetrical with respect to the water surface, so it is inverted. Its principle is the reflection of light, so C is wrong;

D. A shadow is a shadow. When light travels in a straight line and meets an opaque object, the dark area behind the object is called a shadow, so D is correct.

So choose D.