Honeycomb tube-worm reef. Built on sandstone rocks at the low tide margin, Welcombe Mouth, Devon, UK, the reef is made of millions of particles of sand and shell in flattened grains of various colours. They are collected by the tube-worms and glued together with mucus into a colony of individual tubes that, seen at a distance, appear to be a uniform colour. If assembly was random then lighter and darker areas than the norm would be evident. This is an example of camouflage as the reef colour reflects the body colour of the worm not that of the surrounding sands.