Colourful refraction by the surface waves

On June 13th Thorsten Falke from the German North Sea isle "Düne" (near of isle "Helgoland") was walking along the seashore, when he saw criss-cross light structures on the seabed obviously caused by refraction by the surface waves. He had seen the phenomena often before but this time it seemed to be coloured. He decided to paddle out into the water to take pictures. It was difficult to see the colours visually because of the rapid movement of the little waves (only 2 cm "high") but in many of the pictures the colours were evident. The appended picture was taken with a macro lens and shows a shell in 10 cm deep water with a colourful refraction band across it. Because of the macro lens the picture is nearly 2 times life size. Another refraction is located at the upper edge of the picture. If he remembers rightly, the light was coming from the left side and was parallel to the wave crests. The main interest of Thorsten is to observe whether the colourful refraction is seen only when the wave crests are parallel to the light direction or if it is also visible when the crests are at right angles to the sunlight.