Hi I saw your post somewhere online where you asked what those small irregularly shaped "flatter creatures" where.
I cant tell for sure from the photo, but to me those look like rhodoliths.
Rhodoliths are small unattached assemblages of coraline algae. Basically little colonies of free living coral (usually shades of pink and brown). The the living part is just the colored "skin" and the hard part is the animals skeleton. Sea Urchins, fish and molluscs feed on them.
Anyway, that's my guess from the photo....
thanks for that post!