I went on self-funded three day two night trip on a Vat Phou Cruise so I could see Vat Phou, the 4,000 islands and the Pha Pheng Waterfall. The boat, a converted teak carrier, has 10 cabins with accommodation for around 20 people. All up there were only four of us on the cruise, a Swiss lady whose son runs a hotel in Luang Prabang, a German couple- both lawyers- and myself; therefore we were well and truly outnumbered by the staff. I was surprised that they still ran the cruise but the captain explained that running costs still had to be paid and savings from cancelling would have been illusory. Both food and accommodation were top notch and the whole thing was excellent value for money, my only complaint would be that even though it was a cruise we spent most of the time moored to the river bank.
We were picked up in Pakse and transferred to a small river boat, the Mekong there is too shallow for the Vat Phou to navigate, and made our way about 20 km downstream to the boat. After cruising around a bit during lunch we spent the rest of the afternoon at the actual Vat Phou.
The "Vat Phou Temple complex, is a remarkably well-preserved planned landscape more than 1,000 years old. It was shaped to express the Hindu vision of the relationship between nature and humanity, using an axis from mountain top to river bank to lay out a geometric pattern of temples, shrines and waterworks extending over some 10 km. Two planned cities on the banks of the Mekong River are also part of the site, as well as Phou Kao mountain. The whole represents a development ranging from the 5th to 15th centuries, mainly associated with the Khmer Empire." I have to confess I didn't make it up to the top of the temple! See UNESCO.
