The Tonle Sap, or Great Lake, is one of the largest and most important fresh-water systems in southeast Asia. It’s also one of the most interesting. The lake is connected via the Siem Reap River to the Mekong River and is home to a number of communities of ethnic Cham and Vietnamese people who live on houseboats. During the dry season the Siem Reap River flows from the lake, which at that time of year is only about a meter deep, and drains into the Mekong River. During the monsoon season, however, the Siem Reap River reverses direction and flows from the Mekong River into Tonle Sap Lake. The lake grows much larger (by a factor of four or five) and deeper (by a factor of eight or nine), and the people move seasonally from lake to the mouth of one of its feeder rivers and back again, wherever the fishing is best.

We visited during the start of monsoon season, and the river leading to the mouth of the lake was lined with houseboats. (The brown color of the water is due to a high rate of sedimentation, a normal phenomenon of this ecosystem.)

“People here live pretty close to their neighbors,” our guide pointed out. “So do you know what they do if it turns out they and their neighbors don’t get along?”

“What?” we asked.

His eyes gleaming, he said, “They move! Home and all!”

And we were, in fact, lucky enough to see someone in the process of doing just that.

And there weren’t just houseboats. There were also shop-boats of all sorts, and cafe-boats and basketball-court-boats and church-boats. All of these migrate up and down the lake with the people.

There’s even a grocery delivery service.

Since many of the people are fishermen, they work in the evenings and at night, and they rest during the day. And so we saw a lot of people at home, many of whom were sleeping in their hammocks.

At the mouth of the river,we reached the end of the settlement and the open expanse of the lake.