Underwater world: Corals have high primary productivity and can provide numerous organisms  with abundant food resources. Indicator-species like garoupa will also be one of the targets in the reef check.

Over 320 volunteers and divers will shuttle through the mysterious but colourful underwater world in the coming three months to conduct health checks for 'residents' - coral reefs. 

They will survey 32 coral sites in waters stretching from Tung Ping Chau in the north to Ninepin Group in the south, including the eastern part of Hong Kong where corals are densely populated.