THE FIRST I HEARD OF PIMPERNEL ROCK WAS FROM A FRIEND. 'You have to do this dive, it's somewhere on the New South Wales coast near Byron Bay,' he said. 'I'm not sure what it's called, but it's a fantastic pinnacle that rises up from about 40m.
 'Right through the centre is a huge tunnel that leads to a smaller tunnel. It's home to heaps of grey nurse sharks, and wobbies, and in winter, if you're lucky, you might see humpback whales cruising overhead as they migrate north.'
 The dive sounded fantastic, so what was I waiting for? Well, a name and a location would have helped, but these vital details had escaped my friend.
 The following year, a diving colleague heard that I was migrating myself, south from Cairns to Sydney, and diving the NSW coast along my way. He had worked in the industry for seven years and dived some of the world's best sites.
 As we chatted, he became very animated about an 'amazing' pinnacle with a huge cavern and a cave at 42m; a volcanic rock inhabited by heaps of grey nurse and wobbegong sharks.
 It all sounded familiar. This time, I made sure to get a name, and an exact location.
 Just 10 days later, I was jumping aboard an 8.5m Fast Cat owned by Stan Young of Wooli Dive Centre, and heading out over calm seas to the infamous Pimpernel Rock, part of the South Solitary Marine Reserve.
 The rock used to break the surface at low tide, so the story goes, but about 30 years ago a naval vessel ran aground and sliced a piece off it. Deemed too dangerous for fishing, they ended up bombing the whole top off, creating an ideal place for a deco stop on this deep dive.
 There are in fact three steep pinnacles, a large tunnel or cavern (38m at the base) and a small swim-through cave at 42m. The cavern runs through the middle of the rock, about 12m high, 15m wide and 25m long, and resembles a huge cathedral archway. A diver hovering in midwater at the far end, framed by volcanic rock, makes for a breathtaking sight.
 All manner of sea life dwells in this remarkable sanctuary, but the most exciting and abundant are the resident grey nurse sharks (Carcharias taurus). Grey nurses are also known as sand tiger or raggedtooth sharks in Australia, and are not to be confused with that other type of nurse shark that spends much of its time static on the seabed (called the tawny nurse shark here).

Grey nurse sharks are spectacular creatures, 2-3m in length and with long sharp teeth. Divers have seen up to 30 of them on one dive at Pimpernel Rock and, because they're so unused to people, they're pretty friendly. My guide, Peter, got up close to one of them as they glided in to check him out.
 'I was just floating there, hugging the rock and taking in the view, when all of a sudden a face of teeth appeared from around the corner and I realised that it was coming straight at me. It must have come within a few inches of my mask before it twitched its body and turned away,' he said. 'It was pretty cool.'
 What's amazing about these animals is the deafening sonic boom they make when they crack their tails and zoom off into the distance, as often happens when camera flashes go off.
 The first time it happened I got quite a fright, because these fish can really move when they want to.
 You never see them alone, either. Shoals of yellowtails congregate like frenzied groupies around them, hoping to grab a free lunch. And don't forget to look up to the roof of the cavern, because there will be at least five or six raggies swimming around your head.
 Meanwhile, at the bottom, red mowang rest on the rocks, watching inquisitively as divers stare in awe at the shark circus. And the walls of the tunnel are thickly populated with tubastreas and sea urchins, as well as the odd wobbegong skulking in the ledges.
 While the grey nurses may be the draw card at Pimpernel Rock, the most common sharks seen here, and indeed all along the NSW coast, are the wobbegongs (or 'wobbies', as they are affectionately known in Australia).
 These harmless bottom-dwellers litter the pinnacle. Six species can be found in Australian waters, but the most common to Pimpernel are the ornate (Orectolobus ornatus) and the spotted wobbegong (Orectolobus maculates).
 You'll see them lying motionless in trenches, waiting to ambush a tasty fish or lobster. Don't be fooled. They look pretty sluggish but they move like lightning when food is in the offing.
 In Australia, more divers have been bitten by wobbies than by any other shark. And when they bite, they lock their jaw and won't let go.
 In their defence, most attacks are provoked. For some reason, divers have a fixation with trying to pick these little fellas up by their tails. Unfortunately for them, wobbies are among the only sharks that can turn around and bite their own tail - or an unsuspecting diver's hand!

It's only when your computer urges you to go shallower that you take your eyes off the amazing tunnel structure and its large, raggedtoothed residents to appreciate Pimpernel's other attractions.
 As you move up this vast structure to 35m, sponge and whip coral gardens decorate the reef. It's like a big sweetshop full of pastel-coloured lollipops. Boulders are infested with black tree corals, mussels, cowrie shells, soft and hard corals and ascidians. Small-scale and red scorpionfish hang out in little trenches, and bull rays glide past overhangs. Eagle rays and occasionally mantas also cruise the reef.
 There isn't a vacant plot of rock to be seen; everything is competing for space. A few holes offer the only relief, and even these are inhabited by juvenile green morays. They look yellow, but I'm told they're green if you take them out of the water!
 What's the key to Pimpernel's diverse marine ecosystem? Around the Solitary Islands, the warm Queensland current meets the colder currents that form further South. Species associated with the Great Barrier Reef, such as Moorish idols, trumpetfish, butterfly, angelfish and fairy basslets co-exist with temperate seaweeds and fish that like colder climates.
 Schools of pelagics patrol the pinnacle - devilfish, samson, amberjacks, jewfish, trevally, mackerel and bullseyes, as well as black cod, spangled emperor and snapper.
 As you ascend, you'll be entertained by giant kingfish creating a fish-swirl as they dart in and out of schools of yellowtail, looking for a morsel or two.
 And if you're really lucky, you might bump into a few white floating anemones. The Solitaries have the highest concentration of anemones in the world.

Pimpernel Rock is one of those dive sites that people talk about but hardly anyone had dived until recently. Why? Many factors have to come together for a trip to the rock to be successful, says Stan Young, because Pimpernel Rock is isolated, exposed and prone to big swells and strong currents.
 'Every local knows about it, but they can't always find it,' he says. 'It's a small rock, literally in the middle of nowhere. You have to be on the ball and really take note of your sonar.'
 Stan dives the site only when conditions are good. 'You won't believe how quickly they can change. Sometimes the surge and swell is really bad. One minute your reg is free-flowing as you go down the line, the next you're being blown off the rock and can't get back to it.
 'You have to know your stuff. If I think any of my divers aren't up to the conditions, I don't let them in.'
 It's also easy to get caught up by the spectacular life and slip into decompression. I found diving on air very limiting, and when I return I'll be taking nitrox for my second dive.
 If you get to Wooli anticipating diving the Pimpernel, only to have your hopes dashed by bad weather, don't fret. There are plenty of other great dive sites around the Solitary Islands.
 North Solitary, in the marine park reserve, is only seven nautical miles from Wooli, and famous among local divers for the diverse marine life at such sites as Fish Soup, Darcey, the Boulders and Anemone Bay.

Pimpernel Rock is one of Australia's top 10 dives, and on par with any site I've explored in the Coral Sea. It might not have that sea's 30-40m visibility but, boy, does it have a lot of great shark action!
 So when I told my diving colleague that I was writing an article about the site, he was appalled. 'Don't tell them about Pimpernel Rock,' he pleaded. 'Write about Fish Rock Cave instead. Pimpernel's one of our best-kept secrets!' So if anyone asks, you didn't hear it from me. Mum's the word.