Australia's Clearest-Water Dive Sites in External Territories

The top of this list is inland. The Limestone Coast sinkholes and the Nullarbor caves hold groundwater that has been filtered through kilometres of limestone; there is no plankton, no sediment and no swell, so visibility is limited only by the light. Kilsby, Ewens Ponds and Piccaninnie routinely exceed 40 m and the caves exceed 100 m, numbers that no ocean site in Australia can match.

In the sea, clarity comes from distance from the coast and from the open ocean. The outer Great Barrier Reef at the shelf edge (Agincourt, the Ribbons, Osprey), Lord Howe and Balls Pyramid, the Coral Sea atolls and the Rowley Shoals all sit in oceanic water that the coastal rivers never reach. The temperate south has its clear days too, usually after a week of offshore wind in winter, but 20 m is exceptional where 40 m is routine on the outer reef.

Clear water changes how a dive feels and how it should be planned. Depth is hard to judge when the bottom looks close; divers in the sinkholes routinely find themselves deeper than intended, which is why the CDAA sites have hard limits, guides and permits. Buoyancy control matters more, because every fin kick is visible for 50 m and silt in a cave stays suspended for days. And photography is easier and harder: no backscatter, but a scene that stretches further than any strobe can reach.

The sinkholes and Ewens Ponds are diveable year-round with the water a constant 15 °C; a 7 mm suit or a drysuit is standard. The outer reef is clearest from September to November, before the wet-season runoff.