The wedding party are Cambodian, dressed in formal costume in the middle of their vows, with fellow villagers crammed all around them. The wedding crashers, on the other hand, are hardly incognito: nine Westerners in bicycle gear, plus our Cambodian guide.

To be fair, it is the guide who had seen the signs of festivities up ahead and said the Cambodian equivalent of: "It's a wedding. We must pop in and pay our respects."  Like most foreign visitors – and our cycling group contains two Americans, two Italians, two Peruvians, two Australians and a Briton – we are horrified at this impromptu intrusion. How would we like it if a dozen Cambodian guests arrived without invitation cards at our own weddings?

The invited guests make way to let our group have a view of the festivities. We take a few photographs, watch the ceremony for 10 minutes, wish the new couple every happiness, and remount on our bikes, wondering if we have done the right thing.

If the experience seems bizarre, there's more to come. Our scheduled itinerary includes a family pottery business (where I buy a couple of clay piggy banks in the shape of elephants: yes I know Australian coins won't fit through those minuscule slots).

And a palm oil farm where a 63-year old grandfather demonstrates his prowess at climbing 12-metre tall palm trees to milk the pods for the oil he ferments into a vodka-like alcohol (to be honest, the antics he performs as he climbs the death-defying tree suggests he has already consumed copious amounts of his own product).

What we didn't know beforehand was that this village is mourning the death of a much-loved 88-year old woman. Here again we are invited to take part in the funeral ceremony. So we listen to the Buddhist chants of family and friends gathered around the coffin under a marquee, then watch the procession that follows the coffin-bearers, doing several laps  of the funeral pyre before loading the coffin onto the very top. I find it all incredibly moving, even more so for it being totally unexpected.

But we agree to leave before the actual cremation. It's twilight and we want to get back to our ship, the Aqua Mekong, before dark. Had we wanted to stay, it would have caused no offence to our Cambodian hosts.  After generations of warfare, genocide and disaster, the Cambodians now seem to let little bother their enjoyment of life. They are, almost certainly, the most generous people I have ever met, willing to forgive any unintended indiscretion.

For me, this experience,  "One wedding and a funeral," symbolises our seven-night voyage up the mighty Mekong from My Tho, in the Vietnamese delta, to Siam Reap, gateway to the fabulous temples of Angkor in north west Cambodia. The route is hardly a new one. Around a dozen cruise boats already go up and down the river between Vietnam and Cambodia. Still more run cruises confined to one or other side of the border.

And yet the Aqua Mekong, which cost more than $11 million to build, has just joined the fray. At roughly    $1140 a night per person, it is more or less the same voyage you could do for approximately half the price on other vessels. We're on the maiden voyage upstream. So what, if anything, distinguishes the Aqua Mekong from the opposition? And is that worth the extra price?

Aqua Mekong is an elegant gamble by Francesco Galli Zugaro, chief executive and co-founder of Aqua Expeditions which has operated similar adventures along the Amazon for the past seven years. A clue is in the name: Aqua Mekong is more of an elegant expedition than a traditional cruise.

Around 10 per cent of the passengers on his two Aqua ships on the Amazon are Australians  "The fourth largest nationality", he says, "after North Americans, Europeans and South Americans". So he anticipates "at least 15 per cent" of the new venture will be  Australians. So what could anyone booking expect for the extra dosh?

Of course, there is the "ship" itself. This is definitely not a conventional river cruise boat, more a contemporary floating hotel in subtle brown/grey colours, designed to blend in with the Mekong surroundings. Sometimes when we are returning to the Aqua Mekong by motor launch we think we are lost because it is so neatly camouflaged.

Each of the 20 rooms are roughly twice the size of its competitors. Eight have balconies; the others have full cabin river views, with the eight balcony suites having sliding interconnecting doors if a family wants to travel together.

There's a small gym, a large spa with a range of treatments including "traditional Khmer massage" (with or without cream), a plunge pool, adequate upper deck sunbathing areas, a DVD room, adisappointingly tiny library/games room, and,  finally,  a vast lounge/bar/meeting room/lecture hall on the top deck where everyone gathers before or after an adventure.  And yet I forgot to mention one of the signature attractions: the restaurant. Australian chef David Thompson, whose TV series, Thai Street Food With David Thompson, is now screening on SBS, has devised and, subsequently fine-tuned, the exquisitely Asian menu.

This is one of the great points of difference between Aqua Mekong and its rivals: a world-class chef who has painstakingly invented a menu that makes the most of what the Mekong has to offer.  Surely you want to taste the produce of the local areas you are passing through a region, particularly when the freshness of the fish, seafood, free-range chicken and pork is so self-evident from your excursions?

Sadly, on our trip, there are a few complaints (from the Americans and Europeans) that the food is "too spicy" or "not sufficiently Mediterranean". Too bad, I say. Book a cruise in the Med if you want Mediterranean food.  For the record, the lunches and dinners on my visit (when the South-East Asian influence was to the fore, and the breakfasts more Western-conventional) were exquisitely Indo-Chinese: refined, adventurous, delicious.

Our four on-board guides agree. This is another diversion from the Mekong norm. Usually, Mekong river cruises swap guides at the aquatic border. However, Zugaro has appointed four full time, experienced guides. Two are Vietnamese, Tuyen and Yee. Two are Cambodian, Hoeum and Visoth. They declare themselves "brothers" throughout the river passage,  which is remarkable given the recent history of the two countries.

It doesn't take a degree in maths to realise the ratio of four  guides to 40 guests on the Aqua Mekong is 1:10. "The usual ratio on the Mekong is 25:1." says Zugaro. "And our guides continue throughout the entire journey."

It took Zugaro two years to win permission to get the Aqua Mekong adventure afloat. Negotiating with two neighbouring war-tortured countries (whatever your politics) was always going to be a challenging task. To make things more complicated, Zugaro chose to have the Aqua Mekong built in Vietnam but registered under the Cambodian flag. But it is operational now. There are a few minor teething problems, but it is is fully booked out until the end of 2014 and beyond.

My advice? Book the upstream voyage. Vietnam is a beautiful country, but everything you see on the lower Mekong will be surpassed as you move away from the sea – and "civilisation" –  towards Angkor Wat.

Angkor was a city of around one million people in 1100 when London was a European metropolis of perhaps 35,000. Angkor has over 200 temples: we have time to visit only one on our trip because we're not staying overnight. Fortunately, it's the largest and most famous: Angkor Wat. But our entire party wishes we had longer to explore.

Rescued from the jungle by French colonialists/archaeologists in the 19th century, the Angkor complex is now regarded as perhaps the most extraordinary complex of religious constructions in the world: easily the equal of the Egyptian or Mayan pyramids, Machu Picchu or the Temple on the Mount.

But that is the end point of our voyage. We had gathered, from our various hotels, at the Park Hyatt in Ho Chi Minh City, a few metres away from the famous Saigon Opera House, built by the French in 1897. Then we had climbed aboard the Aqua Mekong coach to My Tho, about 90 minutes away.  At My Tho, one of the main ports on the Vietnamese delta, we had boarded the Aqua Mekong, accepted our welcome drinks and been shown to our "suites" (not cabins!).

The  next day, we start our Mekong education. At Cai Be, we visit our first Vietnamese river town, learning from Tuyen, our first guide, how the Mekong can rise and fall 10 metres between low and high season. So that's why the houses along the river bank are all on stilts.

We've already seen the wide-staring eyes painted on the prows of the river boats carrying rice, fruit, vegetables and other produce Vietnam is famous for along the Mekong. Within 10minutes you can tell how laden the boats are. If they are high in the water, they are empty. If they look as if they are going to sink, they're carrying a full load.

As for those threatening visages? "The eyes are to help the navigators steer the right passage," says Tuyen, before adding: "And to ward off the monsters lurking under the river."

After a sumptuous Asian-Australian (Thompson-designed) lunch, we have a couple of hours to unwind before we take our first cycle tour. Aqua Mekong is the first vessel along the river to offer bicycle options, which is the reason we are able to pop in, unannounced, at a wedding, a funeral and other unexpected encounters along the river. And the only reason it can do so is because the ship, built in Vietnam by a Singapore marine company,  comes with four Australian-designed/built 10-seater tenders (or "skiffs" as Zugaro calls them).

Where other Mekong operators rely on local boats to ferry passengers to and from the local villages, Zugaro always wanted his Mekong cruise to visit unexplored places. It may be the same Mekong, the same start and finish destinations, but the Vietnamese captain of the Aqua Mekong has been charged with delivering passengers to unexplored settlements on the way.

Very rarely have I ever been to so many wonderful, picturesque places that have never seen Western tourists before. Let's hope we don't spoil it for those who come after, and that we will always be welcomed to every wedding and every funeral.

Take a look inside the Aqua Mekong in the photo gallery above.

The writer was a guest of Vietnam Airlines and Aqua Expeditions.

TRIP NOTES

MORE INFORMATION

aquaexpeditions.com

GETTING THERE

Vietnam Airlines offers daily return flights from Ho Chi Minh City, with connections to and from Siem Reap or Phnom Penh, with transfers to the Aqua Mekong. If you are joining or departing in Phnom Penh, Vietnam Airlines operates three flights a day between Ho Chi Minh City and Phnom Penh. See www.vietnamairlines.com.

STAYING THERE

Aqua Expeditions operates three, four and seven-night adventures between Ho Chi Minh City and Siem Reap (or vice versa). Cruises include transfers to and from the vessel and meeting points in Ho Chi Minh City and Siem Reap, beverages (non-alcoholic, house wine and beer) and entrance fees en route. Phone 1800 243 152, see aquaexpeditions.com