Rowley Shoals

Everything here runs off a boat and a tide table. Departures leave Broome on fixed dates, the crossing covers close to 300 km of open ocean and eats a night at each end of a roughly week-long trip, and the only land out there is a scatter of low sand cays. Once on site the boat works one atoll for a day or two before moving on. Dive times follow the tidal exchange rather than the clock, so briefings slide around through the week and the days settle into three or four dives plus a night dive off the back deck.

The three atolls are variations on one shape: a shallow, coral-floored lagoon behind a rim that dries on the low tide, a navigable entrance channel, and steep coral on the ocean side. Inside the lagoon it is bright and calm, with coral heads, giant clams and small reef fish in a few metres of water. Outside there is nothing under you but blue. Most of the diving sits inside 30 m either way, so the walls get worked along their upper section rather than pushed deep.

The dive people come for is the lagoon entrance on a running tide. Divers drop at the mouth of the channel and go through with the water, past coral banks and fish holding in the flow, at a speed that leaves no option but to ride it out and get picked up at the far end. There is no fishing fleet based within reach and no land to send runoff onto the reefs, and the atolls carry marine park zoning — Mermaid under Commonwealth management, the two southern reefs inside the Western Australian park.

This suits divers who are comfortable being carried, who can hold a stop in blue water with nothing underneath them, and who bring their own surface marker for the pickup. It also suits people who accept that the itinerary belongs to the weather: there is no alternative site if a swell arrives, no way to shorten the trip and no phone coverage to complain about it. Divers who want short, easy dives, or who mainly shoot macro, will get less out of the cost than those who came for current, sharks and open water.