Introduction to the reef group: There are many reefs in the sea water, and they are colorful, some are bright yellow, and some are dull dark brown. The hard rock surface has been washed away by sea water all year round, showing pores of different depths and sizes. When the tide rises, the seawater hits the reefs in the water again and again, bringing many green aquatic plants and coral branches from the sea, giving the beautiful reefs a new sea-green dress.