The first night of our voyage up the Mekong river, we decid to dock in a tiny village a few hours south of Kampong Cham as the darkness is descending fast.

After a quick stroll, Mike and I return to find Pauraic and John trying to deal with the aforementioned man, who seems to think in no uncertain terms that we need to remain on the boat. Whether we're being kidnapped or it's a stitch up where we have to pay a fistful of dollars for our man's 'protection' in the morning, there's not much for it but to sit down and watch a movie. We sleep uneasily on the cheap net hammocks we got in the central market.

The next morning finances are gloomily assessed. To our surprise however, our selfappointed guardian will not accept a cent for having kept guard all night. His actions seem an eloquent statement that in the midst of the rot of corruption so prevalent in today's Cambodia, some are still not for turning.

The four of us have chartered a boat for five days, our route taking us through the section of the Mekong which meanders on the map like a wisp of cigarette smoke west of Phnom Penh to Kratie. The Cambodian capital is on the tail end of the Tonle Sap river and it's a half an hour by boat to the point where the two rivers collide. Road improvements between Phnom Penh and Kratie have stripped the river of much of its freight and passenger traffic and boat tourism seems as yet a relatively unexploited possibility. It adds, though, to the sense of going into the unknown.

By day, the water of the Mekong is a muddy reddy brown, a seemingly inert surface hiding powerful currents underneath. It is almost unimaginable that in the dry season what is now so fat and bloated dries up to a vast mud plain with just a sliver of water splitting it. None of the four of us are brave enough to risk swimming, until Mike, mostly to amuse a group of children riverside, jumps in one evening. The sight of the big lump of a barang tossing mud on his back and doing handstands seems to be the funniest thing imaginable and they laugh uproariously on the shore.

Kampong Cham, Cambodia's third city, is the site of the only bridge across the Mekong.

The legendary guide, Mr Vannat, brings us to an abandoned airstrip a half hour out of town.

From here American B52s launched countless sorties that rained death across Asia. Meanwhile, we sit on an old lookout tower and take in the surrounding lush countryside. Little swirls of mist are settling sleepily in distant hills as the sun comes down.

Our days are spent in a blissful haze, sitting on the open deck of our nameless boat, listening to music and watching the world go by on either side. We pass innumerable, impossibly rickety-looking fishing boats, with occupants who have that particular serenity of expression that is a feature of this region. We watch them as they crouch down on their haunches, or show unexpected strength hauling in the heavy nets. What they make of the four reddening westerners drinking beer as Daft Punk blares out of the speakers I shall never know, but most politely acknowledge our waves. One fellow even dances exaggeratedly for our benefit, laughing all the while.

Temple tops peep over the tops of trees on either side. Near Kratie there are makeshift stairs all the way from the river side to the top of the hill where a particularly ornate one sits.

As we pass the long jagged clay-coloured Chahio cliffs on the west side I spot our Khmer guide Pagoday pouring a few bottles of water and beer overboard. An offering to the God Hanchey for luck, he explains, shrugging as though he's not entirely convinced. Either way, it seems the least we owe this river, and I chuck in some bread for good measure.

Kratie is a charming little town, its untarnished French colonial-style buildings giving hints of a more prosperous past. We dock and get a moto ride further up river, to see the Irawaddy freshwater dolphins. There are only between 50 and 60 of them left in this part of the river. We take a small boat out to the western side, moor on some bushes and wait.

I don't know what was in the water that day, but those dolphins really put on a performance.

They all but go into formation and start singing show tunes and we return to shore elated.

We've allowed for two days to get back to Phnom Penh but the flow of the river whips us along and we realise we can make it the whole way back before nightfall. Our last sunset in the Mekong is a truly stunning affair . . . bloodred fire lighting up the sky as we come towards the point where she meets the Tonle Sap.

Two more days flowing with her and we'd be in the South China Sea. For a moment it's tempting, but the lights and bustle of Phnom Penh are calling us. As the Mekong retreats into the distance I steal a last glance back, silently promising to take her up on that offer again some other time.

The facts Getting there Joe Walsh Tours in Dublin has the best deals to be found. A flight to Phnom Penh in October was just /800. Call 01 2410800.

Where to stay If you've a tight budget, the Dara Reang Sey Hotel near the riverfront in Phnom Penh is basic but secure and has very helpful staff. A double room is about /7 per night.

Holiday in Cambodia

>>Ignore the rather nondescript outskirts of Phnom Penh . . . Sihanoukville, just a four-hour bus ride from the capital, offers miles of unspoilt beaches and excellent places to eat and drink.

>>The wonders of the temples of Angkor are well documented. Also worth an hour-long drive out of town is the Beng Melea temple, a stunning example of vegetation running riot over an incredible structure. A lot of the time it's deserted, giving the visitor a sense of having discovered it for the first time.

>>The Dead Fish guesthouse in Siem Reap offers an enjoyable stay for the budget traveller, as well as showcasing that particularly Khmer brand of black humour. Bizarrely themed rooms (mine was the 'Lonely Lounge'), free head massages and an excellent restaurant are some of its extras. Just be careful before making your way from the bar to the bedrooms. It's a narrow walkway under which is a vast crocodile pit.

>>Go to a kickboxing event in Phnom Penh. The locals go crazy for it, and the atmosphere in the dilapidated main stadium is electric, particularly when a local lad takes on a Thai.