what creaature builds reefs
Polyp
the mudskippers
A denizen roughly means 'an occupant of', so a reef denizen is any creature living in the reef, so to answer the question ill say starfish.
The Crown of Thorns starfish is the biggest natural threat to the Great Barrier Reef.
A skeleton of a tiny sea creature is a coral reef.
It means underwater structure made by calcium carbonate
Carpenters builds or repairs wooden structures.
kiwi
The Mesoamerican Barrier Reef System stretches from the tip of the Yucatán Peninsula down to the Bay Islands of Honduras. It includes the Belize Barrier Reef. This reef structure is the largest coral reef in the Western Hemisphere and the second largest barrier reef in the world.
model
Reef
Deposits of Coral Rocks