Australia's wet and wild outback

Nine hours north of Darwin, the Cobourg Peninsular is a watery wonderland of marine life and wilderness. Jo Moulds gains access to Australia's best-kept secret

Salt-water crocodiles put most people off diving in the Cobourg Peninsula, a remote area in the north-west corner of Australia's Northern Territory. It remains, as a result, a fairly well-kept secret. Less than 1,500 people visit the park each year, and tourists are required to obtain a special permit to pass through Aboriginal lands. We were there in the name of research, and were keen to dive in a virtually unexplored area which had, apparently, an unparalleled diversity of marine life.

I'd read an article by a fishing journalist which mentioned dugongs (otherwise known as sea cows, or manatees), turtles, dolphins, manta rays and hammerhead sharks. I had wondered how he'd seen hammerhead sharks if he was just fishing from a boat? "Because they come and take the bait off your line," a colleague told me.

In 1983, Cobourg was designated a state marine park; it covers an area of the sea surrounding the Cobourg Peninsula that is the size of Berkshire. But, after initial research into the area's marine biodiversity, it was left to its own devices. Due to the remoteness of its location, more than 15 years passed before any further marine research was conducted.

The few visitors who tend to make the trip to Cobourg are fishing enthusiasts, lured by the reputation it has earned as one of Australia's most pristine and abundant fishing grounds (and Australia is not short of spectacular fishing destinations).

In 1999, a Russian marine biologist, Victor Gomelyuk, was permanently assigned to the park. Gomelyuk now lives year-round at Black Point Ranger Station - a cluster of purpose-built rangers' dwellings that house the hardy staff of the Parks and Wildlife Service NT. He is one of only 12 people who live here through the wet season, which lasts from October to March. Their only face-to-face contact with the outside world during this time is a mail plane which lands once a week, weather allowing.

Here, the threat of cyclones is as common as the almost daily torrential rain. Tourists generally visit during the "dry" - from April to September - when four-wheel-drive vehicles can make their way up from the city of Darwin.

The road trip from Darwin to Cobourg takes nine hours at least. It is believed that Aborigines have lived here for about 40,000 years; they are thought to be some of Australia's few remaining coastal-dwelling indigenous people. The local Aborigines have helped Gomelyuk in his research on the historical and anecdotal stories of fishing and hunting in the area.

We were in Cobourg as volunteers, helping to collect data on fish species. Volunteering turned out to be a fantastic way of seeing places you would not ordinarily get to visit.

On our fortnight trip, we flew north to Cobourg on a six-seater mail plane, along the coastline, watching as Darwin's city buildings receded into seemingly endless bush and mangrove systems, snaking out to reach the Arafura Sea.

Crocodiles can often be seen off the coast as you fly in to land - their heads barely visible above the water, their tails disappearing into the blue. This was the sea we were about to dive in.

While we were there, we went diving off a deserted island. We traced the circumference on foot to investigate the flora and fauna. Gomelyuk carried a "powerhead" - a long, metal, stick-like weapon loaded with a bullet that releases on impact. That was our only reasonable defence against the crocodiles. Apparently, although they live in mangrove swamps or freshwater billabongs, they like to swim out to offshore islands to sun themselves during the day. We were checking that there weren't any present the day we were going to dive.

Gomelyuk was mapping coral reefs: identifying fish species and numbers; monitoring dugong and turtle populations (six endangered sea-turtle species are protected around Cobourg), and assessing the impact of recreational fishing. He noticed that there were quite a few anomalies in the area: there were hardly any butterflyfish species, for example. This was surprising for a tropical area with abundant coral.

The diving in Cobourg is shallow. All the coral reefs in the area grow at less than five metres in depth. Frequent storms and squalls stir up fine silt deposits and the poor visibility (often less than three metres) prevents the sun from penetrating deeper, stemming coral growth. The average dive depth during our fortnight's stay was only three metres.

Despite this, the diving was adrenalin-inducing - getting into the water when you know that there are potentially large, hungry crocodiles lurking nearby is enough to get anyone's heart racing. Add poor visibility and the knowledge that crocodiles are some of the world's most successful predators and you've got the recipe for a hair-raising encounter. Sharks are angels of sweetness and light by comparison.

Underwater, the plus side to diving in Cobourg becomes immediately apparent. I have never seen so many fish - large fish - at such close quarters and so unafraid of divers (which is probably because they've never seen any). Giant sweetlips, mangrove jacks, coral groupers, barracuda, batfish, jewfish and queenfish (a type of trevally and the fisherman's prized catch) were abundant on every dive.

On one outing my buddy signalled, wide-eyed, that he'd just seen a shark. The visibility was only two metres so this was a very close encounter and, judging by the look of surprise in my buddy's eyes, quite a large shark.

From photos that we later used to identify it, it was probably the back end of either a tiger shark or a bronze whaler, not the world's most "human-friendly" shark.

At sunset, while fishing from the pier, we were treated to a series of spectacles.

One evening we saw dolphins playing in the distance. Nearby a shark circled patiently, no doubt hoping to make a meal of the giant trevallies we were trying to catch. The sound of a gentle sigh interrupted our reverie and we looked up to catch a glimpse of a dugong as it surfaced to breathe.

On another night, a large eagle ray swam slowly and silently under the pier, gliding just beneath the surface, giving us time to admire its beauty. On the same day, two manta rays had played nearby, leaping out of the water just a few metres from our boat. These experiences made us realise why Cobourg is such a special place, and how lucky we were to be there.

Little has changed at Cobourg since 1838, when British settlers attempted to establish a community nearby in Port Essington. They abandoned their base after just 11 years as life was just too tough. The red cliffs and the endless white-sand beaches remain untouched and the Arafura Sea, uncompromising and yet so tempting to fishing enthusiasts, provides a serious challenge to divers who might be interested in something a little more than out-of-the-ordinary.

Recreational diving may commence in Cobourg: a local boat-charter operator is interested in offering scuba-diving adventures. Alternatively, you could of course volunteer to help with the marine research, as we did. Not only do you get to see the marvels of Cobourg for free, you will also get the satisfaction of helping with the research efforts that will secure its future.

Cobourg has been described as "one of the last truly wild places in the world", and it is difficult to disagree. There are banteng (wild oxen) that munch on trees at night, antilopine wallaroos, and kamikaze frogs that land on your face in the night if you don't put a mosquito net up to stop them. Cobourg is unforgettable.

TRAVELLER'S GUIDE

SIGNING UP

For more information on volunteering, contact the Parks and Wildlife Service NT (00 61 8 89 995511; www.nt.gov.au/nreta).

GETTING THERE

You have to change planes somewhere to reach Darwin. From the UK, the lowest fares are likely to be on Royal Brunei (020-7584 6660; www.bruneiair.com) from Heathrow via Brunei. Qantas (08457 747767; www.qantas.co.uk) can take you to Singapore, from where its subsidiary, Australian Airlines, takes over.

If you sign up as a volunteer, the Parks and Wildlife Service NT will organise connecting flights to Cobourg (one hour). Otherwise, one-way charter flights cost around A$285 (£122) and can be organised through Direct Air (00 61 8 8945 2099; www.directair.com.au).

Alternatively, visitors can enter Garig Gunak Barlu National Park by four-wheel drive (nine hours); accessible only through the dry season, this road winds through Kakadu National Park and Arnhem Land. Permits are required to enter Arnhem Land, which can be arranged through the Parks and Wildlife Service NT.

DIVING THERE

The water is tropical all year round (24C-31C). A "stinger" suit would be recommended for divers to ward off box jellyfish.

STAYING THERE

Volunteers stay free; the writer stayed in an old school teacher's house on the ranger's station.

Cobourg Beach Huts, Winnellie (00 61 8 8979 0455; www.cobourgbeachhuts.com.au) are sold at A$220 (£95) per night. Campsites are rudimentary but adequate. Contact the Cobourg Peninsula Sanctuary (00 61 8 8999 4814).

MORE INFORMATION

Northern Territory Tourist Commission (09068 633235, calls 60p/min; www.ntholidays.co.uk).