Oyster Reef
Oyster reefs are located in and near shorelines and estuaries. They are particularly prolific close to the mouths of rivers because the water is brackish, or salty, and is less than 10 meters in depth. Oysters thrive in this kind of reef and make their homes in the shells left by other oysters. It is not uncommon for oyster reefs to be massive settlements with astounding numbers of oysters living there. An oyster reef is home to fish and other organisms as well.
Coral Reef
Coral reefs are made up of a mixture of coral and algae. For coral to grow well, it needs to be in water that ranges from 18 degree C to 30 degrees C. It must also have plenty of sunlight. Because of these specific requirements for life, coral reefs are found between the latitudes of 30 degrees north and south. It is in these latitudes where the sea temperatures meet the coral's needs.
Fringing Reef
A fringing reef is a subcategory of the coral reef. It is formed as an underwater platform composed of living coral. The fringing reef starts at the shoreline and continues out to the sea, yet is still in shallow water. Fringing reefs are commonly found around tropical islands and continents. A fringing reef can also form on top of materials such as limestone or volcanic rock,
Barrier Reef
A barrier reef is a specific kind of fringing reef with a lagoon that separates it from the coast or mainland. You can find coral growing on the waters of the lagoon as well as on the seaward reef. The largest reef ecosystem in the world, called the Great Barrier Reef, is off the coast of Australia.
Atoll
When a barrier reef completely or partially encircles an island this is called an Atoll. Some of the reef may rise out of the water and form small islets. Atolls are formed as a result of the slow sinking of oceanic islands. This process takes thousands of years.