Answer
When the duck is reflected in water and forms an image, the reflection differs from a simple inverted view of the duck.
Work Step by Step
For example, try putting a mirror on the floor between you and a short chair. You look directly at the top of the seat, but the mirror shows the underside of the chair. The reflected view is not just an inversion of the straight-ahead view.
The duck reflected in the water is what you would see if you were located as far beneath the water level as you are now (ignoring refraction). You would not see the top of the rock, so the reflection in the water won't show that.
This is shown in Figure 28.5.