Another low tide yesterday evening.  I saw a large clam which had been left behind on the sand, unable to burrow under.  The white tube on the lower right is called a siphon, through which the clam takes in water.

I also saw several mussels covered in barnacles.  I looked closer and these barnacles were still living!  The video shows them moving.

You'll have to look closely to see the clam siphon moving, and the barnacles waving, in this video.