The Northern Territory is a land of extremes — a place where wetlands stretch further than the eye can see and sunsets paint the sky in colours too vivid to capture on camera. Just a few hours east of Darwin lies the Mary River, a wild sanctuary where barramundi leap against the tide, sea eagles hunt overhead and campers fall asleep to the chorus of frogs.

Darwin has its heart-stopping “jumping croc” river cruises, but nothing excites me more than the idea of sleeping under the stars in a place more densely populated by estuarine crocodiles than anywhere else on earth.

Just 150km from Darwin’s five-star waterfront comforts, the prodigious Mary River covets a landscape of mind-boggling size and beauty: lily-fringed lagoons and vast, verdant floodplains, dense monsoon forests and mangrove-fringed tidal reaches that lure big crocs in from the Arafura Sea.

Safeguarded as a national park, the Mary River Wetlands gathers a fan club of anglers, walkers and wildlife watchers, but this sanctuary – I quickly discover – is a primitive place to dwell.

Our family sets up a rustic home base at Shady Camp, stacking firewood and shaking out camp chairs, then heads for the nearby riverbank to enjoy the cool hours before sunset when wildlife emerges to feed. In the late 1980s, a barrage was constructed across the Mary River in an attempt to keep saltwater flow out of the wetland’s precious, but threatened, freshwater habitat upstream.

What this skinny concrete dam fails to do is stop estuarine crocodiles and other determined amphibians from moving up and downriver as they please. So, it’s an incongruous sort of place to find a lineup of anglers standing ankle-deep on the barrage, casting their lines.

Battling barramundi

After the Top End’s long wet season, the run-off begins, draining rivers and wetlands and rushing all that water swiftly back to the sea. The Mary River Wetlands purge their sodden marshes too, gathering up hapless fish in the rapid flow and sending them plunging over the barrage.

Anticipating the frenzy, anglers arrive to pick them off en route, stealing prized catches of barramundi from the salties circling below, their great tails raised, swinging slowly back and forth.

The vigorous rush of water makes this a treacherous place to cast a line, but the punter plonked in his camp chair midstream appears utterly undeterred. I skip nervously past them towards higher ground on the opposite bank and, watching the crocs, try to decide if these apex predators below are waiting for fish or a heftier, human-sized meal.

While all this barramundi chasing is taking place, an astonishing thing happens. Powerful mullet begin to leap upstream, doggedly scaling the barrage against the rushing tide. There are dozens of them – small but determined – and they slowly make ground, forcing their way over the concrete barrier into the freshwater pool above.

A sea eagle suddenly swoops down and snares a fish with its mighty talons, devouring it mere metres away in the low branches of a riverside tree. Cormorants are fishing too, and when the anglers lose interest and move on, a trio of juvenile nankeen night herons descends to fish silently as the sun retreats.

Sunset in the wetlands

Upstream and close by Shady Camp, a short riverside trail flanks the freshwater lagoon, leading us to a viewing shelter where we sit and watch the birds. We spot Jesus birds – light-footed jacanas – that leapfrog effortlessly across the pink lotus lilies, earning their moniker by appearing to walk on water.

Great flocks of magpie geese circle languidly overhead, whistling ducks fly straight on to some faraway roost, and a solitary jabiru forages silently in the shallows. This auditorium is alive with wild sights and sounds: raucous cockatoos noisily stripping the riverside pandanus, rainbow bee-eaters hunting on the wing and frogs croaking from their hiding places on the muddy banks.

Agile wallabies nibble nervously on the grassy verge, while freshwater crocodiles float on the fringes, waiting patiently for their chance to move in. We linger too long and meet the mangrove’s most veracious inhabitant – mosquitoes that descend in a thick, buzzing cloud and send us swatting and slapping on a mad dash back to camp.

When repellent and a smoky campfire fails to dampen the mosquitoes’ appetite, we concede defeat and head to our beds, falling asleep to the drone of them clinging to the mossie-proof screens.

Celebrating Stuart

Sunrise scatters the mossies and our serenity is restored, so we dawdle over our morning coffees before the day’s exploring begins. We take a long walk around Shady Camp, named by pioneering explorer John McDouall Stuart in 1862 after he rested on the banks of the Mary River near the end of his epic, cross-country expedition.

Stuart had pioneered a 3540km-long route from Port Augusta to the then-called Port Darwin that finally opened up Australia’s mysterious interior. After a night spent at Shady Camp, he ended his long journey by reaching the sea, at the site that now immortalises his tremendous feat.

Following in Stuart’s footsteps is, ironically, very much dependent upon the weather. Only when the road dries out enough to allow 4WDs to make the trip can you reach Point Stuart and take a walk. If you get the chance, tackle the rigorous, scenic trail that loops along the bay to Stuart’s Tree Memorial Cairn (6km, three hours return).

With the track still sodden and the gate firmly shut, we take our walking shoes to Point Stuart Wilderness Lodge instead, and set out along the Jimmy Creek Monsoon Forest Walk (1.6km, 30 minutes).

Forest wandering

Cool and shady, this easy track disappears quickly into the forest, crossing crystal-clear streams and winding past verdant palms and giant banyan trees draped with prickly vines. Ferns carpet the forest floor where active orange-footed scrub fowls are busy scraping together their big nesting mounds.

There are mossies hiding from the heat of the day too, but our repellent keeps them at bay and before we know it, this lovely, leisurely walk has ended.

Driving south through the national park, we pull over at Mistake Billabong and stroll to the water’s edge. As one of the Mary River’s few permanent lagoons, the billabong sustains plenty of wildlife. From the shade of its viewing shelter, we spot agile wallabies and floodplain monitors, and a plethora of waterbirds that stalk and hunt and rise in great colourful flocks.

We tackle another easy stroll along Brian Creek Monsoon Forest Walk in less than an hour (2km), before shifting our camp to the spacious Couzens Lookout in time for sunset.

Couzens Lookout

Fringed by water lilies, the water’s surface glassy enough to reflect the moody winter’s sky above, the billabong beneath Couzens Lookout is a magnificent find. We follow buffalo tracks to the water’s edge, searching for floating crocodiles and watching tiny fish amongst the lilies and birds fishing beyond.

At sunset, one of the Top End’s most beautiful landscapes is transformed, its colours made vibrant under a crimson sky and suddenly brought to life by creatures that emerge in the cool of the day.

The campground is picturesque too, with spacious sites, picnic tables, fire pits and wheelchair-accessible toilets close by. Best of all, our nightly campfire manages more successfully than Shady Camp to keep the mossies at bay.

Not only is Couzens Lookout a tranquil place to spend a night, but its nearby boat ramp provides easy access to Rockhole Billabong and a maze of freshwater channels through 30km of wetlands.

On the water

When wintertime temperatures cool the nights and southern travellers return to the north, fresh water draining swiftly into the Mary River’s salty tidal reaches stimulates some of the biggest barramundi catches around Darwin.

There’s spotted saratoga, sooty grunter and tarpon to catch too, reeled in from boats and high banks and, despite all discouragement, the Shady Camp barrage. Towing your own boat to Mary River opens up a whole new world of exploring, allowing you to get out on the water to fish and wildlife-watch at any time of the day.

But if you don’t bring a boat, Point Stuart Wilderness Lodge hires four-person Polycraft vessels and runs daily cruises on Rockhole Billabong — especially accessible from the nearby Couzens Lookout campground. If you’re hankering to haul in your first barramundi, the lodge runs guided fishing safaris that secret you away to little-known fishing holes throughout the wetlands, from Rockhole to Shady Camp and beyond the reef that fringes the river mouth in Chambers Bay.

On the western side of the river, two other companies – Wildlands, and Corroboree Billabong Wetland Cruises – run small, open-boat tours from the ramp at Corroboree Billabong, accessible off the Arnhem Highway (from $60/adult and $40/child).

Book an early morning trip to spot the prolific birdlife emerging to feed and see both species of crocodile hauled out on muddy banks, especially once the tide turns and the day begins to warm up.

The Mary River’s great thriving wetlands are renowned for nurturing wild encounters on some of the most pristine waterways in the Top End. Few other sanctuaries are so accessible and so affordable to explore, and that you can be standing at the water’s edge just a few hours after leaving Darwin makes you wonder how this spot guards its secret so well.

When you go, pack firewood, fishing gear and some marshmallows for your nightly campfires, and time your trip for the dry season when rains stop falling, roads open up and the mosquitoes finally lose their appetites.

Escape routes to Mary River

Go

Mary River National Park is located 150km east of Darwin via the Stuart and Arnhem Highways. To reach Shady Camp, turn off the highway just past Bark Hut Inn and drive 50km north on Point Stuart Road.

Visit

Arrive during the Top End’s cool dry season (May to September) to enjoy comfortable temperatures (20-31˚C), clear skies and access for conventional vehicles. Flooding can close the park at any time from October to April. Entry costs $10/day (half-price for kids) or $30 for a two-week pass (valid in all NT-operated national parks).

Stay

Point Stuart Wilderness Lodge provides lodge rooms (from $255/night) and fan-cooled safari tents (from $215/night) with a restaurant, bar and swimming pool (pointstuart.com.au). National park campgrounds at Couzens Lookout and Shady Camp provide picnic tables, fire pits and toilets, and cost $10/adult/night, $5/child or $25/family (book online, bring plenty of drinking water).

Do

Point Stuart Wilderness Lodge runs wetland cruises from the Rockhole (from $80/adult, $42/child) and hires out four-person Polycraft boats from $285/day (including fuel). For cruises from Corroboree Billabong on the western side of the Mary River (from $60/adult, $40/child), head to wildlands.com.au or wetlandcruises.com.au.

Pack

Fishing rods, camping gear, binoculars, firewood, marshmallows and mosquito repellent.

Launch a boat

There are boat ramps where the Mary River crosses the Arnhem Highway (3km west of the Bark Hut Inn), at the Rockhole, Shady Camp, Mary River Billabong (via Bird Billabong) and at Hardies Crossing and Corroboree Billabong, accessed via Hardies 4WD Track on the Mary River’s western side.

Plan

Find out more at nt.gov.au/parks.