AT THE BAECH WHEN IT IS LOWTIDE
crescent beach.
along the shore of beaches
You are misidentifying the animals as sand dollars (Mellita), when in fact they are 6-holed sea urchins.
Sand dollars are commonly found on many beaches around the world from the Carribean to New Zealand. However, they are often found in California too and many are reported to be found on the beaches near Fort Bragg.
On beaches.
In the sea, the sand dollars are found in groups on a soft muddy or sandy sea bed.
Most sand can be found on beaches and in deserts.
They are found throughout the world on sandy beaches.
Not all of them do but some may live in beaches there.
At first it was not known that the sand dollars are living things. People thought (myth) it was like a large coin and that it was the coin/dollar used by the sea mermaids. It was found on beach sands. hence the name sand dollars.
Sand dunes can be found in deserts, beaches, and anywhere else sand is present.
Iron-sand
You can find Sand Dollars in warm clean ocean waters, inshore yards off the beach. The beach is usually near the opening of a river spilling into the ocean which make the waters nutrient rich. The water may be copper colored due to the river.
I have no idea whatsoever oh by the way ...HI !!