It may be crowded but from a geological point of view it's an anomaly, a good anomaly in the same way Hawaii's North Shore fortuitously creates some of the world's best waves right next to each other.

Extend the scope from, say, the Central Coast to Bawley Point, a distance of roughly 400kms, and you've hands down got more slabs than anywhere in the known surfing world. .

We've written about it before, but granite reefs, though occasionally good, lack the flattened convex shape needed for good slabs - they're steep-sided and drop off very quickly. Coral generally finds an equilibrium that can create perfect waves but not hard-hitting slabs, which create more turbulence and faster weathering (hence making the water deeper). Similarly, limestone wears down to an equilibrium depth allowing approximate symmetry between height of the wave and depth of the water.

Sandstone, however, can create convex reefs with 'tongues' that extend seaward to prime incoming swells. Though it has to be layered just right. At Forster/Pacific Palms the layers run at near 45 degrees which is why there are no real pointbreaks or reefs (Haydens aside), while large swathes of the Sydney coast have layers that are horizontal yet up twenty metres between each layer, meaning when the cliffs erode they form large cubes not ideal for reef structure.

Yet Cenny Coast, Cronulla, Shellharbour, Ulladulla, Bawley Point, all have sandstone bedrock that makes for exceptional slabs. Lots of them.