How does a dead coral compare with living coral?

A Coral Reef is MADE by small animals the look like flowers.

These animals make tubes and shells to live in. The secrete a very hard material almost like concrete. This part of the animal is completely and totally dead. The rest of the animal, the fleshy part, is completely living.

When the animal dies, the hard part is left, and THAT is what we call "coral". Baby animals will attach to this dead part, and as they build shells the coral reef grows bigger.