North-east of Amrum Odde lie many sandbanks, which only emerge from the sea during low tide. These sandbanks, which lie close under the water surface for a long time, form these beautiful ripple structures on their surface. Here you can see the ripples even in the tideways, which are colored green in the picture.
The whole picture is full of ripples! Somehow it looks to me as if you were looking at reptile skin.