You may have had this same experience and wondered what they are?
Well - they are the egg collars of Northern Moon Snails!
Both the Northern Moon Snail and the Shark's Eye Moon Snail create and lay their eggs into these "egg/sand collars".
Here is a close-up of the eggs in the sand collar. The eggs are smaller than the grains of sand on the beach!
For more information on Moon Snails check out these web sites: