I can see what he was trying to do with this. But without a real explanation of how to achieve the water with black gesso, I was lost. My sponge marks didn't look anything like they should have to have a successful stream. 😬 I definitely know why this one isn't very popular on this site!
Using acrylic paint for this required a lot of glazing medium or watering it down to glazing liquidity. Bob used a lot of paint thinner on while painting the rocks.
I do like the brightness of the sky.