Hyper calcified sponge (Petrobiona massiliana)
The small white blobs next to the markers are the sponges.
This is a very rare "living fossil". It was first found in dark caves near Marseille and it was determined to be the only living species of a group of sponges previously known only as fossils.
It is now being researched as its skeleton holds a climate record that might be of use in understanding changes in the marine environment and possibly climate change.