On Saturday I had the opportunity to visit my eldest son's new home which is close to an Adelaide beach. After a tasty lunch we went for a beach walk and one of the shells I found is called a razor shell. It is a sort of triangle with rounded edges. I have put in a link so you can read about it. The fascinating thing about it was that it had a clam shell adhered to it, and small other types of shells adhered to that, and so on for several layers. Then when you turn it to face you, there is a monster face!
Razor fish shell
Look closely to see the sea monster - once you pick out the eyes you can see the face