When the sand shifts and hidden bands of rock emerge from the beach…

 

The sandstone appears freshly scrubbed.

 

Gradually the stone is colonised by algae.  First a few green strands in the sheltered cracks…

 

Then tufts and beards of delicate green weed.

 

Nearer the low tide line, tough wracks soon smother some rocks while others, less hospitable, remain smooth and bare – rock, sand and seaweed in infinite variety..