The Cathedral (Motolang)

The Cathedral is known locally as Motolang and lies against Pura Island, the extinct volcano cone that sits in the middle of the Alor Pantar Strait. Above water a steep rock face drops straight into the sea, and the same shape continues below: huge jumbled boulders give way to a steep wall packed with hard corals, soft corals and sponges. A swim-through with a cave opens at roughly 25 to 30 metres. Divers have found a large tawny nurse shark resting inside it. Thermoclines run through the site and the water can turn noticeably cold, so a thicker wetsuit is often worn here.

The wall rewards slow, close looking. Bargibanti and Pontohi pygmy seahorses have been recorded on it, the latter tucked into Halimeda algae, alongside a blue-ringed octopus and two species of frogfish. Crabs and nudibranchs work the coral, and marble rays turn up on the sand. Beyond the swim-through the reef opens onto colourful soft coral. Pura is volcanic, and at several sites around the island air bubbles seep up through the shallow sand.