As a marine sanctuary, coral reefs are very important to many marine life forms like visible plants and animals and millions of microscopic organisms that live in the micro-spaces and crevices of coral reefs. There are also many zooplankton that resides in it which are essential to the coral reef food chain. According to Dive Asia, coral reefs are, without a doubt, one of the true natural treasures of our earth. They are home to an enormous variety of life forms, which is why they are often compared with tropical rainforests. Coral reefs need sunlight and warm water to exist. As a result, we only find coral reefs between the 30th parallels north and south of the equator. The minimum temperature that tropical corals can exist at is 20 degrees C. The Andaman Sea, which is part of the Indian Ocean, hosts a unique variety of marine life. More than 3000 different types of fish and over 500 unique corals have been identified and cataloged at the Similan Islands to date. Coral reefs in Phuket Island are facing the threat of destruction today. As a result of global warming, more and more of the phenomenon known as “coral bleaching” is also occurring. When bleaching takes place, the symbiotic algae in the corals are expelled and the corals become transparent. When this happens, it becomes possible to see through to the white limestone underneath, hence the name “coral bleaching”. Most of the corals will eventually recover from the bleaching, but if the warmer water temperatures last too long, the corals will be destroyed forever. A further danger facing the coral reef ecosystem is the increase in tourism. Millions of people worldwide spend their leisure time around, on, or in the ocean, particularly on Phuket island. Many reefs show extensive damage from boat anchoring and pollution. DIVE ASIA is a leading proponent of reef preservation and has made the protection of coral reefs one of its highest priorities.