65 million years ago the islands of the Maldives were part of a huge volcanic mountain range. When the volcanoes ceased to be active they submerged sinking at a rate slow enough that coral formations could grow on their rims. This coral growth eventually became the fringing reefs of the atolls. Recent surveys have discovered that the depth of coral on the fringing reef is as much as 2100m (6400ft), a remarkable statistic when you consider a coral massif may grow just 2mm (0.08in) annually.
As the oceanic currents eroded the atolls’ rims they created channels, and today these channels provide some extraordinary diving. The tides of the Indian Ocean flow in and out through the channels, and in so doing concentrate millions and millions of microscopic plant cells, tiny marine animals and larvae, collectively called plankton. This rich soup provides food for many of the reef’s inhabitants. In turn, creatures further up the food chain are attracted from the ocean by the prospect of a good meal, and a rich and diverse marine community builds.
Inside most of the atolls is a complex formation of reefs. A number of these reefs are circular, enclosing a shallow lagoon, others irregular and shallowly submerged. All offer interesting and usually easy diving and excellent snorkelling. Some of the best diving is on submerged reefs called thilas; usually located in the middle of a channels, these rise from the atoll floor to within 10m (33ft) of the surface.