A (big) river runs through it

"My goodness!" exclaimed our Peruvian guide, Victor Coelho, with practised English irony. "This guy should slow down. He's hyperactive." We followed Victor's gaze to a spindly cecropia on the riverbank, where a three-toed sloth was making what was – in sloth terms – a frantic dash for safety. One ludicrously long arm clutched at the humid air before descending in slo-mo to the next branch down. Only once the grappling-hook claws had secured their grip did arm number two follow suit. In the time it took the animal to move just one metre down the trunk, I was able to change my lens and fire off a dozen snaps. I could probably have washed my socks and written a postcard home.

While the laborious descent continued, Victor told us more. Sloths move so slowly, he explained, that more than 100 species of insect make a home in their fur. Even moss and algae thrive among the animal's hairs – which point downwards on its upside-down body in order to speed the run-off from rainforest showers. This bizarre beast, it seems, is more habitat than animal. Mind you, our pace of life was not so very different. Just 24 hours into our exploration of the Amazon and I was already shifting down several gears into sloth mode.

My lethargy was inevitable, perhaps, given the seductive comforts of the Aria. This elegant 32-berth vessel, on which I had just joined an inaugural four-night cruise, was launched by Aqua Expeditions from Peru's jungle capital, Iquitos. Together with its sister ship, the Aqua, it now offers floating accommodation of improbable luxury at the heart of the world's biggest jungle.

The plan was simple. We would make daily explorations into the Belgium-sized wilderness of Samiria National Park in northern Peru, using eight-person skiffs to penetrate the smaller channels and flooded forest. Between excursions we would return for downtime on the Aria, enjoying the fine cuisine, listening to lectures at the bar or simply lounging on the sun deck, pisco sour in hand, as the forest drifted past our bows.

I found it all a bit bewildering at first: on the one hand, the primal thrill of venturing deep into the uncharted wilderness; on the other, the self-indulgence of life on board an exclusive cruise ship, with five-star comforts to reassure even the most bug-phobic urbanite.

But I needed little persuasion. After all, the Amazon has always headed the alphabet of adventure for anyone who, like me, was raised on lurid tales of blowpipe-wielding tribesmen and villain-swallowing anacondas. And now, combined with a comfortable bed and gourmet menu? Bring it on, I thought.

My excitement certainly felt as boy's-own as ever when, having boarded the boat in darkness the night before, I awoke on day one to find floor-to-ceiling rainforest framed by my enormous cabin window. And it wasn't long before we were breakfasted, life-jacketed and perched in the skiffs, skimming across the Marañó* river to slip beneath a tangled curtain of foliage into a hidden blackwater creek.

Cue revelation number one: those riverbanks of towering greenery aren't banks at all. Last week, when I visited, marked the end of the high-water season, when the Amazon basin is flooded for some 350,000 square kilometres – an area larger than the UK. It's not so much a forest, then, as a vast lake full of trees. The water really is black, too: the acid product of all those tannins released by the drowned, decomposing vegetation. Just like a peat bog – but warmer. And with more piranhas.

As we nosed deeper down the secret channels, dry land was nowhere to be found. Tree trunks rose directly from the water, their limbs festooned with epiphytes. Floating logs revolved slowly in barely perceptible currents. Verdant forest lawns ahead turned out to be floating mats of water lettuce, each bearing a microcosmic menagerie of frogs and spiders that scrambled from our path.

Finding wildlife in rainforest isn't as easy as you might imagine, as many a crick-necked naturalist will testify, but Victor and the other Aria guides grew up here. Thus they were immediately on to the slightest clue: sibilant alarm calls that betrayed tiny saddle-backed tamarins among the lianas, or a shaking in the foliage that announced squirrel monkeys overhead. And when larger animals proved elusive – the Amazon, after all, is not the open African plains – they focused on the smaller stuff, from bromeliads flowering in the canopy to dazzling blue morpho butterflies flitting through the gloom.

Birds, meanwhile, were everywhere. Peru is home to an astonishing 1,800 species, of which the majority are in the rainforest. Kingfishers dashed up and down the waterways, herons alighted on dead branches, toucans lurched through the canopy, and various parrots – from white-winged parakeets dashing overhead to garish blue-and-gold macaws growling conversationally from the treetops – kept up a constant screechy chorus.

For me, simply entering the jungle was thrill enough: creeping into that infinite cathedral of green in all its mind-boggling shades, forms and textures; feeling that spine-tingling sense of the immensity that lurked beyond our vision.

But just as we were beginning to feel we'd left civilisation behind, our skiff whisked us out of the trees and back to the main channel, where the dark water of the forest spilt into the pale brown of the river like Indian ink in a cup of tea. And soon we were pulling up alongside the Aria. A chilled glass of fresh camu camu juice – a jungle speciality – awaited us as we clambered on board, with a cinnamon-scented face towel to mop our fevered brows and an air-conditioned cabin in which to change for lunch.

Peru's cuisine is today hailed by many as the best in South America, and the Aria's imaginative menus are the inspiration of Pedro-Miguel Schiaffino, celebrated chef and owner of Lima's five-star Malabar restaurant. Schiaffino's aim on the river was to blend authentic Amazonian ingredients, such as forest fruits and river fish, with the best culinary ideas from around the world. Highlights included such delights as – brace yourself – chicken consommé with yucca and banana dumplings, shrimp with coconut-corn sauce, and marapate fish with stewed daikon.

Small wonder, then, that by day two of our cruise, gluttony was fast overhauling sloth as the deadliest onboard sin. But, ever attentive to the wellbeing of its guests, the Aria comes equipped with a gym. Under normal circumstances, I confess, the inside of a gym seems as scary and impenetrable to me as any rainforest, but pounding the treadmill while an ever-changing jungle panorama slipped past the window had a novelty that helped dull the pain.

Back on the skiffs, each day's excursions brought something new. Straight after our speeding sloth came a hoatzin: a prehistoric-looking, spiky-crested bird that is one of the weirder species on the planet. Victor explained how youngsters are born with claws on their wings, and how adults process fermenting leaves in their crop and thus stink perpetually of compost. Next up were red howler monkeys. I'd already heard their throaty roar resounding over the forest at dawn – a noise that rivals that of lions as the loudest of any land mammal. Now we saw the thick-furred, chestnut-coloured primates clamouring acrobatically through the canopy and dangling from their prehensile tails.

And best of all were Amazon river dolphins. Known locally as, botos, these freshwater cetaceans are a striking pink – especially the older individuals – and use powerful echolocation to track down fish in the murky water. Their appearance was always a surprise: sometimes announced by a loud splash, at other times a sigh-like exhalation, but invariably behind us, allowing just a tantalising glimpse. Once I watched a small group feeding mid-river as I reclined on the sun deck, slivers of pink gleaming in the brown water whenever they broke the surface.

Then there were all the beasts that eluded us, but the very thought of which made the forest seem even more enticing: the rare Amazonian manatees, which surface only for a gloop of air beneath the cover of the water lettuce; the jaguars, which – according to head guide Juan Tejada – are spotted just two or three times a year ("so you might be the lucky one"); and the anacondas, giant serpents of legend.

We nearly met an anaconda. Spotting the imprint of its massive coils pressed into the floating vegetation where it had been lying just moments earlier, we cut the engine and scrutinised the tangle. No monster snake appeared, but Victor spied a baby fer-de-lance – Latin America's most feared snake – draped innocently across a raft of water lettuce. The prospect of meeting either species quickly scotched the idea of a refreshing dip for anyone as yet undeterred by the piranhas and electric eels.

After lunch on day three we reached the confluence of the Marañó* and Ucayali rivers, marking the birthplace of the Amazon proper. By now we were beginning to see more river traffic: log rafts carrying people, dogs and chickens; dugouts laden with bananas. These boats were a reminder that communities also live along the Amazon. And to find out more, we hopped into the skiffs and paid a visit to the village of San Miguel, home to a community of rivereños – or river people.

We moored beside the dugouts and wandered among the wooden buildings, all of them perched on stilts that raised them above the flood. The village was coated in mud, still glistening where the floodwaters had most recently subsided. A vigorous game of football hurtled past on a pitch that was still half submerged. Meanwhile the villagers gathered on a patch of dry land to spread out their curios – animals, bowls and other artefacts carved from balsa or fashioned from seedpods – and the shoppers among our party got down to business.

Such tourist experiences can sometimes feel unpleasantly voyeuristic. And yet at San Miguel I didn't feel burdened with that customary "us and them" guilt. There was poverty, yes, but also a sense of an industrious and self-reliant community living from the land – or water – in the only conditions they had ever known, and for which they were better equipped than anyone else on the planet. And the outside world was not absent: following the muffled bass of a stereo system down a line of planks that doubled as a high street, I found the Toucan Bar, where football posters lined the walls, and beers – admittedly, not necessarily ice-cold – lined the shelves.

Aqua Expeditions is working closely with these riverbank communities. As well as fuelling the local economy by encouraging a handicraft industry and other ecotourism spin-offs, it provides free medical supplies and a travelling doctor who makes regular calls. Meanwhile, the Aqua naturalists are working with the park authorities to teach and encourage the more sustainable use of forest resources, including, for example, a new technique for harvesting palm fruits without felling the tree and so depriving macaws of vital nest holes. Wild animal products, once a regrettable staple of tourist knick-knacks in this area, are now seldom seen.

We ended that day watching the sun set over a backwater lagoon, as fishing bats swooped across the water and the ripples of river dolphins lapped against our skiff. The only light was from the canopy of stars above us. It was one of those timeless wilderness moments.

Such moments do not, of course, tell the whole story. Wilderness? Just a few miles downriver the Aria was lit up like a Christmas tree, promising hot showers, a sumptuous dinner and a ride home to our real worlds. Timelessness? We read every week about how the Amazon is changing irrevocably, as the forests are whittled away and the outside world makes its demands.

On our last day back in Iquitos, we visited the extraordinary floating community of Belen, where over 33,000 rivereños have taken their aquatic lifestyle to the doorstep of the city. This Venice of the jungle, complete with churches on stilts, floating barbecues, taxi dugouts and a dedicated radio station, was living, bustling proof that the Amazon cannot stand still.

As our plane left Iquitos and soared above the trees, I watched the forest's green carpet roll out to each horizon, and it seemed that if anywhere was big enough to slow down the plunderings of modernity, it was surely the Peruvian Amazon. The plants keep growing, the river keeps flowing and we can only hope that change – when it comes – keeps sloth time.

Travel essentials: Peruvian Amazon

Getting there

* Bales Worldwide (0845 057 0600; balesworldwide.com) offers a similar week-long itinerary in Peru from £4,095 per person.

* The price includes international and domestic return flights, transfers, three nights' B&B accommodation at the Orient-Express Miraflores Park Hotel in Lima and a four-night full-board cruise onboard the new M/V Aria with all excursions and activities.

* There are no direct flights between the UK and Peru. Lima is served from a range of UK airports via Amsterdam with KLM (08705 074074; klm.com); from Heathrow via Miami by British Airways/American Airlines (0844 493 0787; ba.com); and from Heathrow via Madrid with Iberia (0870 609 0500; iberia.com).

Sailing there

* M/V Aria is operated by Aqua Expeditions ( aquaexpeditions.com).

More information

* Peru Tourist Board: peru.travel