Coral is actually the shell of very small animals called polyps.

In some reefs the polyps take the calcium and carbon dioxide from the sea water and turns them into limestone.

When the polyps die they leave their shell behind and new polyps grow on top.

Coral reefs grow very slowly.

There are two types of coral, soft coral and hard coral.

Click on the coral that you think is hard coral.

Question:

3) What are polyps?