What the diving is like
One destination on this site, but four kinds of diving that share very little except the country, and a trip normally does one of them rather than several. The tropical east is the Great Barrier Reef and, beyond it, the Coral Sea. The reef itself is a lagoon-and-ribbon system dived from Cairns and Port Douglas on day boats and liveaboards, in warm water with the usual Indo-Pacific reef fauna and good coral in the areas that have escaped the last bleaching events. The Coral Sea reefs, further offshore, are steeper, clearer and hold more sharks. The tropical west is Ningaloo, a fringing reef that runs along the coast for 260 km with the drop-off close enough to swim to from the beach. It is dived for aggregations rather than for the reef: whale sharks from March to July, humpback whales from August to October, and manta rays through much of the year. The temperate south is a different fauna and a different water temperature. South Australia, Victoria and Tasmania hold kelp and weed beds with leafy and weedy seadragons, giant cuttlefish, handfish and a large number of endemic species that occur nowhere else on this site. Water is 12 to 20 °C and a drysuit or a thick wetsuit is normal. The muck is under the jetties. Jetty diving is an Australian speciality — Edithburgh, Rapid Bay, Blairgowrie and Busselton in the south, and the Nelson Bay and Sydney sites on the east coast — and it produces the same kind of animal a Lembeh dive does: pygmy pipehorses, frogfish, octopus, nudibranchs and seahorses on a soft or structured bottom rather than on reef.
The shape of a day
Depends entirely on which Australia. The Great Barrier Reef and Coral Sea are boat diving, either a day trip of two to three dives or a liveaboard; the outer reef is far enough offshore that a day trip is a long day. Ningaloo is day boats out of Exmouth and Coral Bay, with the whale shark trips run as a separate full-day operation using a spotter aircraft. The southern jetties are shore dives that can be done at any hour, and are dived at night as a matter of course. The southern boat diving is weather-limited and trips are cancelled often.
Getting there
Cairns for the Great Barrier Reef and the Coral Sea; Learmonth for Ningaloo; Adelaide, Melbourne or Hobart for the south, with a drive at the end of most of them. Distances inside Australia are large and internal flights are usually cheaper than the time spent driving.
When to come
The tropical north is dived June to October, outside the wet season and outside the stinger season, when box jellyfish and irukandji make unprotected swimming inadvisable in coastal water. Whale sharks at Ningaloo run March to July. The southern states are dived in their summer, December to April, when the water is warmest and the weather most settled; the giant cuttlefish aggregation at Whyalla is the exception and happens in the southern winter, May to August.
Fees and what is not included
The Great Barrier Reef Marine Park charges a daily environmental management charge, collected by the operator and added to the trip price. Ningaloo Marine Park and the southern marine parks have their own arrangements. Amounts change, so check what the operator is quoting rather than what was true last season.