Help! What are these??

[Leslie Tabor]

If you zoom waaayyy in they look like baby trochus snails. Or limpets?

 

[Sophie"s mom]

Looks like a couple different things to me, as another said , some are collinesta snails, harmless filter feeders, the other, does not move, and are really tiny? If so they are spirorbid worms, which are also harmless filter feeders. Both can grow to great numbers though