Calcium carbonate formations (above) called gour or rimstone pools, form in the rainy season as water seeps in and collects in ponds, over time leaving complex deposits.
Explorer John Pollack's team found cube-shaped "cave pearls" in some of the cave's gour formations that were up to 12.6 inches (32 centimeters) in circumferencepotentially a world record, he said.
Pollack's team chose February, the middle of Laos's dry season, for its 2008 expedition to the Xe Bang Fai River cave.
Still river flow was measured at 12.8 cubic yards (9.8 cubic meters) per second.
During the August-September monsoon, the Xe Bang Fai River roars through the cave at up to 1,300 cubic yards (1,000 cubic meters) per second.
Photograph by Dave Bunnell