I took this photograph while shooting with some friends a few years ago just north of the Pigeon Point Light House in California. I was showing a group of students how to use GND filters when I took this photograph.
I used a hard Edge GND filter to balance out the light between the sky and the ground. The filter edge was aligned just below the rocks (accounting for the darkening of the rock at the very top). I chose this composition in order to fill the lower part of the frame with green moss.
You can see light reflecting from the pool as well as the rocks beneath the surface.