On a visit last August, the low tide shore in Swansea Bay was covered with amazing natural sand ripple patterns as far as the eye could see. Amongst the lans and grooves of the beach surface was the tell-tale evidence of the huge population of marine worms living buried in the wet sediments. The worms were most likely to have been the common lug worm (Arenicola marina) which live in u-shaped tubes below the surface with the entrance hole for water and sand food marked by a circular pit and the exit hole for getting rid of waste covered by the worm cast. The worm in the hole sifts through the sand particles for pieces of organic debris to eat and then the digested sand waste is extruded from the burrow in long tubular strands coiled like a walnut whip. There was a great deal of variation in the density of worm casts in different areas; and the colour and texture of the sand varied according to the water content, the shore level, the proportion of mud and organic material, and the direction of the light.