Mushroom Soft Coral (Anthomastus ritteri)
This coral is soft, meaning that it does not produce a calcium carbonate skeleton. Unlike the rigid, or hard, corals that thrive in shallow, sunlit, low nutrient areas, soft corals thrive in regions with less light and high nutrients. They typically feed on any free floating food in the water column. This type of mushroom soft coral is pink with a circular and oblong shaped fleshy body with tentacle-like projections coming out of it. The corals are found on the carbonate cobbles found on the sea floor.
Reference:
http://www.realmonstrosities.com/2012/03/mushroom-soft-coral.html