Patterns on stone

I went on a regular walk from The Loons to Birsay village today. The marsh was pretty quiet, though there was a flock of about two hundred curlew and a hen harrier hunting. At Marwick I explored a piece of shore I seemed to have missed before, from Sand Geo south to Outshore Point. I have passed along the cliff path lots but not the shore itself. The tide was low and I found a lot of beatiful wave- carved stone and sand-floored sea caves. This image is of a pettern left by a sea plant on the bedrock. I thought it might be a fossil at first. More shots here.