You don't have to share Seacrest's rather bizarre idea of excitement to agree that groundwater is a big deal. It's the source of drinking water for half the U.S. population. Nebraska, for example, floats on water, sitting atop a gigantic sponge of sand and gravel that contains several aquifers. The High Plains is the largest--174,000 square miles of water-soaked substrata averaging 200 feet thick that extends from Nebraska's Sand Hills south through Kansas into northern Texas. There's enough water in it to fill Lakes Huron and Erie combined. In places, farmers can drill a dozen feet or so into the richest soil in America, erect a center-pivot sprinkler system, and watch their corn grow as high as an elephant's eye.

But not without paying a dangerous price. To get bumper crops, farmers depend on pesticides and nitrogen fertilizers, which can seep below the surface and contaminate the groundwater. That's why Seacrest, a 45-year-old Nebraska native, launched the Groundwater Foundation, an organization that uses everything from publications to educational festivals to teach people about threats to the water they drink. Started on a shoestring in 1985 in Lincoln, the Foundation has built a national network of activists determined to protect the fountains of life.

Her crusade began almost by accident, the result of a near miss with tragedy. In 1982 her first-born son, Logan, came down with an intestinal illness that made it very difficult for him to digest food. Desperately sick, the baby was rushed to the hospital five times before he was a year old, thinner and weaker each time. Seacrest and her husband feared they were going to lose him. A little later, an article about a local increase in the number of cases of leukemia and non-Hodgkin's lymphoma cast suspicion on possible carcinogens in drinking water. Seacrest scribbled a letter to the epidemiologist behind the research asking for more information. Expecting a "condescending reply," she received instead a challenge to learn everything she could about groundwater pollution and make other people aware.

"I quit everything," she recalls. "I immersed myself in studying groundwater. Immersed-hey, that's a great word for it." After two years of solitary reading, attending conferences, and questioning scientists ("I'd be a hydrogeologist if I could do it all over again."), Seacrest decided it was time to share her knowledge. And Logan-now a college freshman-had recovered, even though the cause of his illness was never discovered.