STRANGE CLOUDS

Please, look at these 2 pictures:

 
PICTURE #1
PICTURE #2

Images slightly 'doctored' (contrast enhanced, luminosity dimished and rotations).
The picture are 'clicable' for full view.


It looks similar. Does it not?

Actually,  the picture #1 is a picture of the sky, someting like:
Sorry,  I can't put my hand on the original personal picture :((.


The second picture is from this scan:


Now, while the  undulations (waves)  in the water can be easily explained, how could
you explain the similar phenomenon in the sky?