I was a little wary at first when I heard Earth River's Fu trip described as "the world's wildest, most comfortable river trip. "The word comfortable threw me. Not that I was looking to be uncomfortable on my seven days in Patagonia, but I also didn't want to be insulated from the wild I came in search of. I didn't want to be catered to, waited on hand and foot. I wanted to get wet. I wanted butterflies in my stomach. I wanted adrenaline. I soon found out I had nothing to fear.

My journey began in the fishing town of Puerto Montt, a three-hour flight south from Santiago, where I met my fellow rafters. We were an interesting group. A banker and his wife, three lawyers, a biology teacher, an entrepreneur, and an entire family, its members ranging in age from 15 to 74. One group member was six months pregnant. From there we caught a tiny plane for our flight south along the coast - the massive 800,000-acre Pumalin Park stretched out beneath us on the left side of the plane - all old-growth and fjord. We landed in the village of Chaiten, a place more outpost than town, and headed into the mountains. A three-hour drive later (amazingly without passing a single car), we found ourselves at Earth River's private base camp, 300 acres of meadows and forest perched 100 feet over the Fu, dominated by the imposing Tres Monjas (the "Three Nuns"), a 7,000-foot mountain topped with three towering granite spires. The camp comes equipped with showers, a kitchen, tents, and a wonderful wood-burning hot tub, but once I crested the bluff and saw the Fu waiting below, nothing else seemed to matter. The river was all I could think about.

The first thing I noticed was the color. In its more tranquil spots, the Fu is a deep blue-green - like the crayon color a child might imagine for water. When the canyon walls close on the river like a vice, the water mixes with pure white froth to become almost a pastel seafoam-green, the kind you see on hot rods.

The river itself boasts 12 Class Five rapids, the wildest rapids considered safe to raft. These rapids, with names like Inferno, Purgatorio, and Terminator, demand to be taken seriously. Terminator is the epitome, says David Kashinski, a river guide who has spent 14 years guiding boats through the Grand Canyon, Mexico, and Belize, and now guiding the Fu. The consequences are huge.

It was rapids like Terminator and Inferno that prevented a raft descent of the river until 1991. An attempt to raft the Fu in 1985 almost ended tragically when one of the rafts was torn to pieces by the river. Hertz and Earth River made the first complete raft descent in 1991, and the first commercial descent the following year. Thanks to a new kind of raft, specially designed by Hertz, and endless scouting, both trips - and every Earth River descent since - were without incident. Hertz is obsessed with the safety of his customers, constantly drilling customers about what to expect and how to handle it. Hertz also uses safety rafts that stay with the boats in case any paddler is ejected.