No one move! Everybody freeze!" The park ranger is trying to make herself heard over the crash of waves and the static on her walkie-talkie. "We have a turtle."

Though many people in our 30-strong group carry torches, we are forbidden to switch them on. We halt, collectively hold our breath and peer into the darkness.

Clusters of stars are our only source of light and my eyes strain to make out the silhouette of a huge loggerhead turtle as she emerges from the sea and crawls awkwardly yet purposefully towards the dunes. But something has spooked her. Suddenly she stops, turns and starts lumbering back towards the surf.

"Oh no, no, no." Our guide's frustration is palpable.

"She's done a U-turn."

We're standing on Mon Repos Beach, about 14 kilometres east of Bundaberg. These brown-sugar sands are part of a 45-hectare conservation park that supports the largest concentration of nesting sea turtles on the eastern Australian mainland and acts as one of the two largest loggerhead turtle rookeries in the South Pacific.

Our nocturnal excursion is part of a turtle-watching program managed by the Queensland Parks and Wildlife Service, instituted in 1985 after increasing crowds threatened the successful breeding of these endangered marine reptiles.

The fine print on our tickets states: "To protect the animals and preserve your safety as a guest, all turtle watching guidelines must be followed at all times. If you do not follow these guidelines you may be asked to leave the Mon Repos Turtle Rookery at any time and without notice."

So we're doing exactly as we're told. Our guide orders us to huddle close together, walk close to the shoreline, keep our torches and our digital cameras off. We creep along like ghosts, whispering, holding hands, bumping into each other in the dark. I am carrying a sleepy three-year-old on my hip. My five-year-old trails solemnly behind, clutching a toy turtle we picked up in the souvenir shop.

The salty air whips my hair about my eyes. I'm so close to the shoreline a wave breaks over my ankles, soaking my shoes and socks. The occasionally fraught communication between staff and visitors reveals what a devilishly difficult task it is, balancing people's curiosity for this seasonal spectacle while leaving nesting turtles undisturbed.

Many things can put them off laying their eggs and send them back into the waves: bright lights, loud, low-frequency noise (the human voice doesn't bother them, though) and sudden movement.

A message crackles out of a walkie-talkie somewhere nearby. "She's body pitting."

Further up the beach, above the high-water mark, a loggerhead turtle is using all four flippers to dig herself a body pit, or large depression, in the sand.

We are summoned to form a circle and watch her when she begins to excavate the egg chamber.

I'm not entirely sure what I'm looking at for the first few minutes. Actually, it looks a bit obscene.

A staffer has delicately positioned a torch and it's throwing soft light over her rear end as slowly, methodically, patiently, she digs out a vertical, pear-shaped cavity with her hind flippers.

It doesn't seem like many minutes have passed before someone shouts: "She's started to lay."

A ripple of excitement races through our group as the eggs begin to emerge - perfect white spheres, squidgy-looking, gelatinous, almost glowing, like giant pearls.

It's at this point, we're told, that nesting turtles are least vulnerable to disturbance, and so we're allowed to turn on our torches and take photographs. The announcement prompts a considerable amount of pushing and shoving as people behind us muscle in for a closer view.

A couple of us topple over like dominoes, someone complains about a kicked shin, my spectacles fall off in the scuffle, and despite much scrabbling around in the stalky dune grass the glasses are nowhere to be found.

The thought crosses my mind that I might have a bit of difficulty driving back to our motel later, but by squinting fiercely I can still make out what's happening.

I am transfixed by the dignity and grace of the turtle. As a hush falls over the group, I feel I could watch her forever. Even my sons, usually loud and hyperactive, have been rendered silent, reflective, watchful.

She drops more and more eggs into the chamber. It's not uncommon for loggerheads to lay more than 100 eggs at a time, but she stops at 62.

In the torchlight I can see her whole body now, her huge head, her broad segmented carapace (shell) crusted with barnacles, her four flippers, the distinctive beak that evolved among her ancestors 200 million years ago, in the absence of teeth, to work like a vice.

And then there are her huge, black eyes that seem to be weeping salty tears.

I twist with sudden shame. I am struck by the sense of having intruded upon a moment in this turtle's life that should have been private, secret, cloaked in darkness.

IT'S not until the next day, browsing through the glossy guide I picked up in the souvenir shop, that I learn it wasn't our presence that made her weep. This teary-eyed effect is created by special salt glands beside the tear duct that excrete the large quantities of salt naturally consumed by sea turtles.

The Queensland Turtle Research Program, which identifies, marks and tags turtles to protect the species and learn more about their life cycle, has been operating at Mon Repos since 1968.

Senior principal conservation officer with the parks service, Dr Col Limpus, said figures from this nesting season indicated the critical decline in loggerhead numbers over the past five years had slowed.

This season researchers were also thrilled to witness the return of the world's longest-studied sea turtle, a flatback that returned for at least the 11th time since being tagged in 1971.

HOWEVER, the old girl we're observing tonight is T82007, who was tagged at Mon Repos in her first breeding season in 1989. Now she's an estimated 45 years old and the eggs she's just laid are her last of four clutches for the season.

She pauses momentarily after the last egg drops into the chamber, and then begins to cover the nest, using her powerful flippers to flick sand into the faces of the people who pushed in front of me earlier. Oh, sweet revenge.

Our circle breaks apart and we make a path for her to return to the ocean.

I've been so entranced by the spectacle unfolding on the dunes that I haven't noticed the yellow moon rising above the horizon. It means we have a bit more light on the journey back, but must halt several times to allow other turtles emerging from the surf to make their way up the beach.

"Where's the lady who lost her glasses?" one of the rangers calls out.

She returns them to me. The frames are bent and the lenses are scratched. The miracle of watching this prehistoric creature pass on her genetic code is about to be overshadowed by the mundane irritations of life, but then I feel a little hand tugging on mine.

"Mum," my five-year-old whispers as he tries to stifle a yawn. It's past 10 o'clock and I realise we've been on the beach for almost three hours, though it felt like a heartbeat. He grins up at me. "Mum, that was so cool."

Destination Turtle Beach

* WHEN The turtle-watching season at Mon Repos runs from November to March. At the start of the season turtles can be watched laying their eggs and towards the end of the season hatchlings can be spotted scampering down to the water. Visitors are reminded that sea turtles are wild animals and do not appear on command and, on rare occasions, may not appear at all.

*HOW For bookings, phone Coral Coast Visitor Information Centre on (07) 4153 8888. As tours are split into small groups, buy your tickets as early as possible to avoid a long wait on the night. Children can relive the memories later at the Turtle Tracks playground on nearby Bargara Beach. For more information, see the Environmental Protection Agency website www.epa.qld.gov.au