The Great Barrier Reef is composed of over 2,900 individual reefs.
That figure describes a connected reef system rather than one continuous coral structure. Individual reefs are separated by channels, lagoons, sand cays, and deeper areas, yet together they form the world’s largest coral reef ecosystem. The system also includes roughly 900 islands and stretches for more than 2,300 kilometres.
Each reef is built largely by coral polyps—tiny animals that secrete calcium-carbonate skeletons. Over generations, those skeletons accumulate and create the complex structures used by fish, turtles, seabirds, molluscs, and countless other organisms.
The number 29,000 is a tempting error because it reverses the scale of the answer, while 900 refers approximately to the number of islands rather than reefs. Counts can vary depending on survey boundaries and whether Torres Strait reefs and shoals are included, but 2,900 is the standard figure used for the Great Barrier Reef World Heritage Area.