This is edited from Steve Lague of the West (24 November 2009).  Wish I'd been there to write it!

If we don't get to do or see anything else, it won't matter, it's already been worthwhile." That was the comment as we powered back to the 24m catamaran Odyssey, anchored inside Clerke Reef as the sun was setting on the first of a seven-day diving cruise at the Rowley Shoals.

He was sitting on the gunwale of a 12m dive tender, still on a high. On our first day, we had dived at a site called the Aquarium, drift snorkelled on an outgoing 10m tide and swum with a humpback whale while she fed her calf. 

The Rowley Shoals is made up of three coral atolls on the edge of the continental shelf about 260km west-north-west of Broome. They were named in 1818 by Captain Philip Parker King. He named Mermaid Reef, the most north-western of the three atolls, after his ship. The middle shoal was named Clerke Reef after Captain Clerke, who had reported it from a whaler some time between 1800 and 1809, while the south-western shoal was dubbed Imperieuse Reef after the vessel from which it was sighted by Captain Rowley in 1800.

All three atolls, which are each about 85sqkm, rise from very deep water with near-vertical sides that form shallow lagoons. Mermaid Reef rises from 440m, Clerke from 390m and Imperieuse from 230m.

They are renowned for their virtually untouched coral gardens, giant clams, inquisitive potato cod and abundant fish life. There are more than 230 species of coral, including 28 different species of staghorn, and 688 species of fish, including sharks that inhabit the shoals.  Clerke and Imperieuse reefs were declared marine parks in 1990, with the size of the parks increased four-fold in 2004. There are still areas at both these locations where fishing is allowed. Mermaid Reef has been declared a Marine National Nature Reserve and no fishing is allowed. Since 1977 charter boats have been taking fishing and diving enthusiasts to this remote location.

It is a 16-hour cruise from Broome over a stretch of water that can become both very rough and windy, restricting the season to October and November.  It is this isolation that ensures the Rowley Shoals remains one of the most pristine coral atolls in the world. It also means that fewer than 250 "tourists" visit the region each year.

After a long night and morning of cruising, fortunately for us on calm water, the first sign of the atoll was a slim white line on the horizon. The line is Bedwell Island, a small sand island that is home to one of only two colonies of red-tailed tropicbirds in WA, and the only land we will see for the next seven days. There is also a small island at Imperieuse atoll which is the most heavily fished and the only one of the three atolls that does not have access to the lagoon.

As we closed in on Clerke Reef, and Bedwell Island, the colour of the water started to change. It reminded me of the waters around Rottnest Island, only the blues are more vivid and the water clearer.  The destination is a site called The Aquarium, the only dive site inside the atoll and one of the shallowest. Falling back into the water was like easing into a cool bath on a hot summer's day and the water was about as clear, with amazing visibility up to 40m.

For the next six days we dived at least three times a day, and on two days added night dives to the itinerary. Despite the extreme depths of water we kept our dives to a maximum of 30m, which was more than enough to thoroughly explore the ever-changing landscape that includes vertical walls, gorges, swim-throughs and big caves. Most were also drift dives, where we allowed the outgoing, or incoming, tide to waft us along the outer wall, exploring on the way. 

The variety of corals, range of colours and abundance of fish life in all sizes and colours at the Aquarium was something I had never seen. The beauty of these natural wonders is enhanced by soft corals in every imaginable colour, massive gorgonians and coral forests that are home to an unbelievable variety of fish. Trying to adequately describe the fish life is difficult.

The shallower water is dominated by tropical fish, with pelagics also cruising just under the surface with sharks up to 3m and in healthy numbers, patrolling the vast schools. The first encounter with a black or white-tipped shark takes your breath away. Like most of the other fish at the Rowley Shoals, they simply ignore you, going about their business, even feeding on other fish. 

There were also giant clams, big turtles, eels, and in certain areas gentle, giant potato cod. The swim with the humpback whale was an unexpected bonus of the trip.