Keeping the rock transparent was not working, so I decided to just paint it opaque with acrylic white and watercolor paint. Putting the rock in shadow emphasizes the area around the rock as the center of interest. I was also able to change the shape so that it did not look like a “submarine” –which bothered me from the beginning.
At the risk of isolating a color, I put some dark green foliage near the rock to give it some “life”.
Making just one object or area opaque could destroy the unity of the painting, so putting it in shadow helps by putting it in a different lighting.
On to the next subject!