The subject of painting water reflections keeps coming up in my teaching and I want to write a more complete guide than I've managed in individual conversations.

Physics of reflection: the angle of incidence equals the angle of reflection. You see in a mirror what is at the same angle on the opposite side of the mirror's normal. For water, this means you see what's directly above the reflection point.

The practical implication: a reflection in still water is a vertical flip of what's above the water surface. A reflection of a mountain includes the mountain's lower slopes, not its peak, if the mountain is distant and the water is close.

Distortion and movement: moving water creates ripple distortions that stretch reflections horizontally. The amount of distortion follows the wave size. Small ripples produce small horizontal smear. Large waves produce reflections broken into fragments.

Color shift: the reflected image is slightly darker and more saturated than the direct view. The water surface absorbs some light in the reflection path. This is subtle but perceptible.

Fresnel effect: at grazing angles, water becomes a near-perfect mirror. At steep angles (looking directly down), the water is more transparent and you see through to the bottom. Vary the reflectivity based on viewer angle.