I can see the eyes just above the surface of the water, blinking in the spotlight – not moving, just looking and waiting. The sun has gone down and the night calls of the birds and animals sound out, trilling and whooping, echoing across in the jungle.
We sit silently in our canoe in the dark, the motor off as the occasional soft splash of the paddle sends ripples across the dark water. There's another set of eyes near by, another and more still.
I am perched in a very small, rather vulnerable low boat in the Amazon, surrounded by alligators and of course, beneath the surface, hundreds of razor-teethed piranha.
"You can see how big the caiman are by the space between the eyes," our guide Eliaquim says as his lamp attached to a car battery picks out the lurking reptiles.
He slowly moves our 12-man canoe towards the shore and suddenly plunges his hand into the water with the speed of a cheetah.
Eliaquim has thrown something in the boat. "It's probably a little fish," I tell other members of the group closer to the front. "I expect it's jumped back out."
How wrong I was. There's splashing at the bottom of the canoe, a scuttle and a shriek from fellow traveller Ange, who's sitting further up than me.
The broad grin on Eliaquim's face says it all. "It's only a baby," he declares as he picks up the alligator.
It may be a youngster, but it's over a foot long and its teeth look capable of gnashing anything in sight.
The creature is returned to his no-doubt furious mother and we are back on our way.
Our boat safari on the edges of the Rio Negro began as the sun was high in the sky and ended under the stars. We'd seen brown throated three-toed sloths sleeping in the tops of cotton trees, dragonflies skimming over the waters, parrots swooping overhead and squirrel monkeys jumping from branch to branch.
Eliaquim, born in the Amazon basin, called out to the birds, whistling and making low noises with the back of his throat, as our boat drifted through the lush-green foliage.
It was high water season and what looked like entire trees were in fact only the tops, meaning we could paddle our boat through the flooded islands.
Butterflies danced above. It was winter in Brazil but the air was hot and balmy.
Our stay in the rustic Acajatuba jungle lodge was the highlight of a stunning three week adventure. We'd already experienced the buzz of Rio de Janeiro, as well as the mighty Iguacu Falls in the south west which were rather less than spectacular this season.
The 250-plus waterfalls, heralded as better than Niagara Falls, were in fact mostly dry.
It was due, I was told, to the La Nina phenomenon – drought caused by the extensive cooling of the central and eastern Pacific – and I was seeing the canyon in a way most other people never get to.
Mysterious river
The sights of Salvador, the lively capital of the Bahia state, also beckoned, but it was the Amazon adventure that we anticipated most keenly. Stretching for more than 4,000 miles from the Andes to the sea, the river is the world's second longest – beaten only by the Nile – and the rainforest is the largest on the planet.
The sheer vastness of the Amazon – and dangers associated with it – held immense appeal for me.
"It's a mysterious river, the Amazon," Eliaquim told us. "When you live on the side of the jungle, you risk your life a little bit – piranha, anaconda, alligators."
We travelled five hours upstream towards the lodge, starting at the Amazon's Meeting of the Waters near Manaus.
The dark black Rio Negro runs curiously alongside the tea-coloured Rio Solimoes, the differences in temperature and sediment preventing them from mixing.
As our boat chugged towards our wooden hutted dwelling in the Anavilhanas archipelago, we were told cheerily: "If you don't like the animals, they have brooms in reception."
The main palm-tree covered wooden lodge which overlooked the river was connected to small sleeping huts by a network of footbridges, policed by rather loud parrot.
At night, there were no noisy electric generators to drown out the jungle sounds and just dimly lit kerosene lamps guided our way.
The first night, my husband and I checked our rooms fanatically for unwelcome insects.
By the second night, we were sleeping under the stars in hammocks with the lodge's resident squirrel monkey for company.
Creepy crawlies
The eyes of the caiman could still be seen glistening in the water, but we slept soundly anyway.
You get used to the creepy crawlies, well most of them, and mosquitoes don't survive near the acidic waters of the Rio Negro.
Thankfully, we were blissfully unaware that the tarantula that was "found" on the roof earlier in the evening had actually been "lost" again.
But he didn't bother us and we didn't bother him.
We took a jungle walk through the humid vegetation. Eliaquim's helper Francisco came too, machete in hand in case we encountered any threatening wildlife.
Protecting the Amazon rainforest is a huge environmental concern.
In the past three years, nearly 70,000 square kilometres of the forest has been destroyed and smoke from burning trees pushed Brazil into the top four of global greenhouse gas producers in 2004.
Although the destruction continues, the government has pledged its commitment to preventing illegal logging.
Brazil's President Lula has insisted the reduction in the rate of deforestation by more than 30 per cent in 2005 was the best result of the last nine years.
Local guides like Eliaquim are doing their bit by adapting their walks to protect the environment.
"We keep to this same trail now as it's environmentally sound. We don't chop the trees down," he told us.
His knowledge of the jungle was immense and he enchanted us with legends of the Lost City, the fabled Amazonian King of limitless riches and the Amazonian women.
He showed us how he learned to fend for himself deep in the forests – apparently a man can survive on four brazil nuts and a dollop of honey a day.
We saw the fruits and leaves used by local tribes for medicinal purposes – kumara for earache and copiaibi for antibiotics – and were told how firefly lava from a palm tree are a useful source of protein.
Every now and then, we heard the call "Carnivorous fire ants. Quick. Quick. Quick" and we moved sharpishly across the trail in our sturdy boots.
Later we tried our hand at piranha fishing, hoping to catch some of the famous fish.
"If you fall in, you're okay... as long as you're not bleeding," we were told.
Francisco caught several of the fearsome specimen. I caught none, although I did manage to hook a few underwater branches.
Heading back to the lodge in the dark, I asked Eliaquim how he found his way through trees and waters when they all looked the same.
"It's like a city – this way, that way. But in the city, you know what's going to happen – not here. It's in my head, a map.'"
He pointed some distance into the water at a tiny ripple I can hardly see: "Over there, see, a school of fish.'"
Does he ever tire of the Amazon? "No," he shakes his head with a smile. "Every day is different."

TRAVEL FACTS
l Laura Elston travelled to Brazil with The Adventure Company, and its Worldwide 2007 programme offers a 15-Day Brazilian Adventure from £1949 per person. The 18-Day Brazilian Adventure plus Pantanal Extension costs from £2448 per person. There is also a local payment of 300US dollars (£170) to cover on-the-ground expenses. Holidays available March-October.
l Prices include flights (ex-Heathrow and domestic), all transportation, accommodation, some meals and services of group leader. UK connections from £95 return.
l The Adventure Company has a responsible tourism policy and travels in small groups, using local-style accommodation, local transport and guides.
l Enquiries: 01420 541 007/ www.adventurecompany.co.uk