Yesterday, I happened to be at Parsteiner See for work.
At first, the sea was completely calm and the only waves were the ones we made doing our photo shoots, like so:
Other than that, the lake was completely calm.
But then suddenly, I spotted a breeze going over the lake. It becomes visible in the dark areas with higher surface roughness, where capillary waves have formed.
As the wind keeps blowing over the capillary wave area, those waves grow and then at some point become “regular” gravity waves, that travel out of the region where they are directly forced by the wind. See below: In the background you still see the area with higher surface roughness, whereas in the foreground gravity waves are coming towards the shore.
As the wind keeps blowing over the surface, forming capillary waves over larger and larger areas, those areas all show up as darker and rougher.
And the cute little waves keep coming to the shore :-)