Here it is with all of the polyps closed. You can see the stony body of the coral, with small "teeth" on the edge of the polyp area.
Two close-ups of the polyps. Note how translucent they are, with white tips. Further note that the stony body of the coral is now completely hidden.
Sometimes the polyps can become very thin indeed. I have no idea why this occurs. It does give you some idea of how much of the "body" of the coral's polyps is in fact water.