What is a circular or horse shoe-shaped coral reef?

A circular or horseshoe-shaped coral reef, often referred to as a lagoonal or atoll reef, is a type of coral formation that typically encircles a lagoon, creating a sheltered area of water. These reefs are formed from the accumulated calcium carbonate skeletons of coral polyps and often develop in tropical ocean waters. The horseshoe shape can result from geological processes, including the sinking of volcanic islands, while the central lagoon provides a unique ecosystem for various marine life. Such reefs are crucial for biodiversity, coastal protection, and fisheries.