You are on an ocean reef. look down at your body. You have become a coral. An important part of this underwater ecosystem. look around at your new home. This is a healthy reef populated with a variety of different plants and animals and several different species of coral, including you. To survive coral need to build and maintain their skeleton. The first step is to collect the basic building blocks: calcium and carbonate ions. Use your polyp arm to grab one of each types of ions around you. These ions are combined to form calcium carbonate, the main component of your coral skeleton. You will need to continue collecting ions to maintain your skeleton and stay healthy.