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Cyrene Reef is home to a wonderful range of corals, Soft, hard, leathery. of different colours and sizes. The clip shows a massive Brown boulder hard coral with Jurong Island in the background. This coral had Mermaid's Fan seaweed growing on top in the crater as well along with the green-white finger algae (?).

More reading on corals :-
wildsingapore.com/chekjawa/text/c510.htm
Hard corals belong to the same group as sea anemones. While sea anemones are large solitary polyps, corals are tiny polyps that are linked each other in a colony. Each coral polyp produces a tiny external skeleton made up of calcium carbonate. This skeleton protects them from danger and provides support. Huge coral reefs are made up of the joined skeletons of countless tiny polyps, living ones growing over the skeletons of dead ones. The various shapes and forms of hard corals arise from the way the polyps join to one another.

Hard food: Hard corals are carnivores. The coral polyps have tiny tentacles with stinging cells to capture food. Large polyps might take small fish, while smaller ones feed on plankton or collect finer particles using mucus films and strands. Most coral polyps only extend their tentacles to feed at night, and remain retracted in their skeletons during the day.

All reef-building hard corals also have an additional source of food as they harbour zooxanthellae (symbiotic single-celled algae) inside their bodies. The algae can carry out photosynthesis and shares the food and oxygen produced with the coral polyp. The coral in turn provides protection and simple minerals. It is believed this additional source of nutrients from the zooxanthellae help hard corals produce their hard skeletons and thus expand the size of the colony faster.

Coral Babies: Hard corals generally reproduce asexually: new polyps bud off and enlarge the colony. A piece of living hard coral that breaks off may continue to grow into a separate coral.

However, they also reproduce sexually. A polyp may produce sperm or eggs, but usually only either one at a time. Eggs and sperm are released simultaneously for external fertilisation. Mass spawning occurs once, sometimes twice, a year in reefs. During this time, many species may spawn at the same time, resulting in an upward rising 'snow' of eggs and sperm. The eggs develop into free-swimming larvae that drift with the plankton before settling down to start a new colonies. Here is a fascinating photo of a coral larva on Image Quest 3-D Marine Library

Role in the habitat: Hard corals are important reef builders. Coral reefs provide homes for small animals and are a haven and nursery for ocean-going creatures. Reefs also protect the shoreline from strong waves, storms and erosion.