We took this boat, the Mekong Express, from Phnom Penh to Siem Reap during monsoon season. It's an interesting journey up the Tonle Sap river to Tonle Sap lake, past thousands of acres of flooded lowlands. The photo above is from out in the middle of Tonle Sap, with the Cambodian flag and its depiction of Angkor Wat flying off the back of the boat.

The captain's Buddha statue (right) watched over the controls, and it was smooth hydroplaning all the way to Chrong Kneish outside Siem Reap.

Tonle Sap has an unusual annual cycle, due to its location upstream on a tributary (Tonle Sap River) of the massive Mekong River, in an area where the terrain is extremely flat. Each year during the monsoon season, the Mekong floods and water backs up the Tonle Sap River, reversing its flow. The Tonle Sap River in turn floods the lake of Tonle Sap in the middle of Cambodia, greatly increasing its size. During the dry season, the swollen Tonle Sap flows back down the river into the Mekong, and the lake shrinks to its smallest size just before the next monsoon flood season.

This natural ebb and flow helps moderate the flooding Mekong River and reduces its flood stage throughout the delta area downstream in Vietnam, while creating an abundant crop of fish and rice in Cambodia by flooding millions of acres of fertile land each year. The fishing village of Chrong Kneish must re-locate twice each year when the size of Tonle Sap changes.