Excursion to Coral islands in Mahatma Gandhi Marine National Park and cruising on glass bottom boat with excellent view of coral colonies under water. Coral reefs exist only in warm ocean waters and are built from a unique type of coral called a hermatypic coral that are a symbiotic combination of a coral animal and an organism called zooxanthellae. It is the unique relationship between these two species that allows coral reefs to grow and exist year after year. Classic coral reef formations begin at an oceanic hotspot near bordering a tropical island and gradually change through thousands of years from a fringing reef, to a barrier reef.