Refractive caustic network

The image shows the so-called refractive caustic network. A wavy water surface (the sea, in this image) projects patterns of sunlight onto nearby surfaces (the bottom, in this image). The surface of the water acts as a series of positive and negative lenses. The positive ones focus sunlight onto the bottom while the negative ones refract light out of the beam. As in this image we are facing the sun and we look at the water surface at a narrow angle, dispersion of light from networks at the bottom at the water-air interface shows flashes of colours.