Matt Damon's Waterworks

"I was thunderstruck," Damon recalled. "Her whole life would literally revolve around collecting water for the day." It was changed by a single well.

There is a tendency among Serious Washington Types to disdain celebrity activists and their pet projects, even as we angle to get our pictures taken with them. (Thanks, Matt. Impressed the kids.)

But what is unusual about Damon's undertaking is its seriousness of purpose, absence of heart-tugging victims, and strategic approach. Water isn't sexy. Diarrhea isn't a fun topic. When Damon talks about "the dignity that comes with a toilet," he comes off as the Harvard student he once was, not one of People's Sexiest Men Alive.

The theory of Water.org is not, as CEO Gary White explained, the traditional "charity-driven model" of addressing the problem simply by using cash to "drill more wells.

Instead of top-down charity, which will never be enough, Water.org's notion is bottom-up sustainability. It enlists communities to plan, contribute to, and manage water projects, and helps arrange and guarantee WaterCredit -- micro-loans to households for clean water and toilets.

White argues that these loans make financial sense. With the financing to purchase access to water, people can work at their jobs instead of devoting hours to obtaining water. In more urban areas, the loans can free them from paying above-market prices to a "water mafia" that charges a premium to those who can't afford to be hooked into the local utility.

The group now operates in Africa, the Indian subcontinent, and South and Central America, building community latrines in the slums of Bangladesh or communal wells in Haiti.

"We've had the answers to clean water for 100 years," Damon said. "Imagine if we cured AIDS or cancer and millions of kids were still dying from it."