It's taken 5 years but I have finally found the answer to a question I raised in a previous post. I've been reading John Muir's book First Summer in the Sierra and he mentions seeing what he calls "windrows" on a lake. These lines of foam turn out to be what I've seen on lakes too. They are odd because whilst wavefronts form perpendicular to wind direction, these windrows form parallel to wind direction and I couldn't see a mechanism to do this. Turns out it is called Langmuir circulation. Now I need to work out how the wind makes these vortices under the surface of the water.
