The Irrawaddy dolphin is a not quite a River dolphin as its normal habitat lies near the coast and delta areas, it is found in river such as the Ganges, the Mekong and the Ayeyarwady River (Irrawaddy River) from where it gets its name. The Irrawaddy Dolphin has a lifespan of about 30 years and can reach about 130kg in weight and about 2.5m in length. It has a rounded head and a flat nose and is classified as a critically endangered species with only about 100 left in total. There are a few clusters of dolphins around the Laos / Cambodian border on the Lower Mekong, which can be seen by taking a kayaking tour.
Xplore-Asia runs a one day kayaking tour through the wetlands of Si Pan Don in Laos, around the Mekong Fault Line. It is possible to spot a few dolphins whilst on the trip as they reside just below the waterfalls on the Cambodian side of the river. The trip starts from Don Det or Don Khone and you kayak to the old French railway bridge, before leaving your kayaks and walking to see Liphi waterfall.
The waterfalls in this region are all part of the Mekong Fault line and are were formed due to the different types of rock beds that exist. The upper basin is made of harder limestone where as the lower basin is a softer sandstone formation. This results in erosion of the basin downstream, creating some magnificent waterfalls to see. Some are small rapids but others are extremely powerful, with Khon Pha Peng waterfall being the largest and is sometimes referred to as the Niagara of South East Asia. The waterfalls span the entire width of the Mekong which in the rainy season could be as much as 13km wide.
After visiting the Liphi waterfall walk a little further downstream to where the put in is and start kayaking in the calmer water towards the Cambodian border. To see the dolphins you actually cross onto the Cambodian side of the river. The Cambodian immigration has even set up a nice dolphin spotting area where you can buy drinks and sit in the shade. They do however charge a dollar for the privilege of dolphin spotting on their side of the border, but no visa is necessary.
Whilst sitting in Cambodia lunch is arranged and you can take a short break to relax and take in this mighty river. The dolphins don't seem to mind the kayak's and swim about normally. There are about 10 dolphins left in this area and a few more further down stream in Kratie (Cambodia). The best time to see them is in the morning or afternoon due to the heat and they seem to surface more in cooler temperatures.
After lunch continue kayaking back across the river to the Laos side and from there it is another 4km further to the Laos village of Veun Kham; a border town. Whilst kayaking you will see the Laos Island of Don Khone the southern tip of this Island is known as Han Khone. At Han Khone the French built a ferry terminal to receive goods carried past the waterfall by train, they also built a ferry dock on Don Det and the idea was that the boats would dock above the waterfall and the goods would be transported below the waterfall by train where another ferry would pick them up. This way the French could have a river route all the way to China, the idea was good in theory but didn't work for very long.
On arrival in Veun Kham, transportation will be waiting to tack you back to Mekong's largest waterfall, Khon Pha Pheng, after seeing this waterfall travel by car and then a short boat trip back to the Islands or on request you can continue into Cambodia.

More information on travel and tours can be found at http://www.xplore-asia.com