Deep in a cave, on a branch of Black Coral ,we found this large mass of Sea Frost, a form of Colonial Serpulid Worm.
Y-Caves, Jackson Bay, Little Cayman Island - Depth 125 feet or 38 meters
 

* The above image was taken in an interesting marine environment.  At Jackson Bay in Little Cayman Island, we dived in a series of underwater caves called locally Y-Caves.  Tidal movement caused very swift currents to run through the caves, and dives had to be timed carefully. There was an abundance of invertebrate  life.  We especially remember the feather-like Hydroids (Sertularella speciosa), By the time each dive was over, our diving suits were filled with hydroid stinging cells, and were a source of severe itching.  Among this unusual proliferation of invertebrates, we found everywhere great quantities of white Sea Frost; that is, of the Colonial Serpulid Worm (Filograna implexa).  In the above image, large stems of Black Coral  (Antipathes sp.) served as a base for one mass of Sea Frost over a meter in size.   Y-Caves, Jackson Bay, Little Cayman Island - Depth 125 feet or 38 meters