I first noticed this about 6 weeks ago and it was about the size of a dime , and now it's about the size of a quarter.
http://i1073.photobucket.com/albums/...C86B299979.jpg
This morning I found it on the sand bed a few inches below where it normally sits on the rock.
http://i1073.photobucket.com/albums/...C86DF91841.jpg
Does anyone know what this is?