I'm working on an illustration of Alpha Centauri B b for Astronomy magazine. Here is what I have so far.
The main reason for showing this is the fact that the middle ground---the landscape between the foreground rocks and the distant hills on the horizon---was accomplished in its entirety (including all the rock-like features and other textures) with two shaders: a water shader and a surface layer.
The water shader's parameters were: Roughness 0.01, Wave Scale 300, Wind Patch Effect 5, Wind Patch size 100. Transparency, reflectivity, etc. are set to zero.
The surface layer only applies a color to the water layer.