what is the meaning of “Fringing reef” in law of the sea, LOSC and customary international law

As used in UNCLOS Articles 6 and 47(7), “fringing reef ” means a reef attached directly to the shore or continental land mass, or located in their immediate vicinity.

Comment
In LOAC-governed situations under the “other rules of international law” clauses in UNCLOS, a different definition may apply. The same may be the situation if the UN Charter supersedes UNCLOS or if jus cogens norms apply. Consolidated Glossary ¶ 66 defines “fringing reef ” as “[a] reef attached directly to the shore or continental land mass, or located in
their immediate vicinity.”
UNCLOS Article 6 says that in the cases of islands on atolls or islands having fringing reefs, the baseline for measuring the territorial sea’s breadth is the seaward low-water line of the reef, as shown by the appropriate signal on charts the coastal State officially recognizes. Article 47(7) says that to compute the water-land ratio under Article 47(1), land areas may include waters lying within islands’ and atolls’ fringing reefs, including that part of a steepsided oceanic plateau enclosed or nearly enclosed by a chain of limestone islands and drying reefs lying on the plateau perimeter.