When you first consider such a journey, it will be all about the destination. An extraordinary introduction to life in rural Vietnam and Cambodia can be topped and tailed with must-see destinations such as Hanoi, Hue, Ho Chi Minh City and Siem Reap for the amazing temples at Angkor Wat. And we cannot recommend strongly enough that you visit as soon as you can - a burgeoning tourist industry in both countries means that things will change very quickly.
But once you have decided that this is your destination, then it is time to consider who you will travel with, and when you look at the options, you will find you have plenty of choice...
Best for outstanding value: AmaDara, AmaWaterways
124 guests, 52 crew, minimum suite size of 251 square feet, and an amazing fly-free bonus currently on offer for 2018: book now!
Best for expedition activity: Aqua Mekong, Aqua Expeditions
40 guests, 30 crew including four guides, suites of 320 square feet; this is the most luxurious operator on the river, with the highest number of included tours and a variety of equipment including their own skiffs, bicycles and kayaks.
Best for unique itineraries: Mekong Pandaw, Pandaw River Expeditions
48 guests, crew includes two guides, cabin size 170 square feet, operating a unique itinerary including Kratie and the Mekong dolphins.
Best for spacious accommodation: Scenic Spirit, Scenic River Cruising
68 guests, 60 crew, butler service, suites from 344 square feet (entry level), Australian style touring with many pre- and post-cruise options.
Best for an organised land and cruise tour: Viking Mekong, Viking River Cruises
56 guests, cabins from 168 square feet, a standard 15 day fly/cruise/tour programme means everything is arranged to the last detail.
Things to note...
The Mekong water levels are highest during the months from August to November, so itineraries may differ at this time of year. Note that for the majority of the year vessels are not able to reach Siem Reap, so if you are planning a visit to Angkor Wat, you will have a long journey by road, or alternatively depending on the itinerary you may be able to fly from Phnom Penh.
Crossing the border from Vietnam to Cambodia and vice versa can be very time-consuming, so check what the cruise operator offers in terms of excursions on the day of the border crossing. Have they good plans to avoid a tedious wait? At present no visa is required for Vietnam (do check because this can always change) but one is needed for Cambodia. How you obtain it depends on where you are entering Cambodia, so make sure you discuss this with us.
Temperatures are highest in March and April, whilst the 'dry' season is relatively short (November to February) but you can in fact travel on the Mekong for most of the year - check carefully, some operators do not sail from April to July, and arguably for good reason.