GRAND CANYON, Ariz. – Like a liquid freight train that's jumped its tracks, the Colorado River careers toward the canyon's far wall. Beyond, it shakes and churns down a channel choked with submerged boulders. Between those rocks and the hard place froths enough hydrological mayhem to flip the Queen Mary.

Expedition leader Bill Bruchak guides our small boat toward the left side of the flow. With a series of hefty pulls, he rows stern-first into the bedlam. Engulfed in turbulence, Mr. Bruchak yanks an oar, and we pirouette to go with the current.

Ahead is a wave taller than a house. As we graze its side, water arcs down, filling the foot wells 15 inches deep. Rolling tail waves follow. The boat bucks through each swell with all onboard screaming "Yee-haw!"

DAN LEETH/Special Contributor

Bill Bruchak rows as passengers hang on through Granite Rapids.

View larger More photos Photo store

We finally reach the eddy at the rapid's end, and I'm beaming. House Rock Rapid has just given me an exhilarating taste of how dories cruise through whitewater.

The sports cars of commercial river running, dories are made from wood, foam and fiberglass. They're about 18 feet long and 56 inches wide and comfortably hold four passengers and an oarsman. A flat bottom and upturned ends make them easy to steer on the river, and because they have rigid hulls, they don't flex with the waves as rubber rafts will. Instead, a sharp prow splits the water in a way that makes even riffles exciting. Unlike inflatables, however, these rigid-walled craft can crack on rocks, so dory drivers must carefully plot routes through rapids.

On this Grand Canyon Dories journey through the length of the canyon, we have four boats for 16 clients, rowed by a three-man, one-woman crew of seasoned guides. The bulk of our gear travels aboard two baggage rafts.

Calm stretches between rapids on the Colorado River in Arizona provide time to relax and reflect.

Our first camp lies on a riverside beach two miles below the rapid. In a drill repeated for 17 nights, everyone unloads gear and waterproof "dry bags." While we seek sleeping sites, the cooking team begins preparing dinner in a portable kitchen. The boatmen assemble water-purification and hand-washing stations then find a secluded yet scenic spot for the portable potty.

We spend evenings circled around a campfire. The Milky Way shimmers overhead, lighting the gaps between inky canyon walls. Most mornings, I awaken to the descending notes of a canyon wren. After a hot breakfast, we load boats and head downstream.

Rapids occur near the mouths of side canyons where flash floods have washed rocks and rolled boulders into the river. We porpoise through most. If the boat hits waves straight on, the prow shoots high into the air with nothing but blue above the bow.

Grand Canyon cataracts are rated on a 10-point technical scale, with 1 being a dancing riffle and 10 a slavering ogre ready to devour anything floating through. I develop my own rating system based on how many inches of water are in the foot well at a rapid's end.

Although pros operate the oars, dory passengers play a part in running rapids. We are responsible for a maneuver that helps keep the boats from tipping.

"If a big wave's coming right at the side of the boat, you want to lean into it," says guide Elena Kirschner. "That means you're going to get wet and cold, but it's a lot less wet and cold than swimming in the river."

Fortunately, dories seldom flip, and unlike rafts, they are easy to turn right side up.

Dories have rigid hulls that don't flex with the waves.

If rapids provide the river's caffeine, flat stretches are its herbal tea. In the calm between the cataracts, we relax as oars stroke the water in metronome rhythm. "If this was all flat water, I'd like it just as much," says oarsman Kurt Brooks.

Although we stop at the canyon's famous spots, they aren't what prove most memorable. It's the secret places. We climb to overlooks and hike side canyons to waterfall grottos. We see where geologic faults have bent rock as if it were taffy. We examine prehistoric petroglyphs, pictographs and Indian ruins, as well as remains left by miners, railroad surveyors and would-be dam builders.

Conventional civilization lies in abeyance. Only on Day 8 when we reach Phantom Ranch, an inner-canyon lodge, is our wilderness interrupted. There, surrounded by hikers and mule riders, we buy lemonade, T-shirts and postcards. Escaping back into the wild, we camp for the night below Horn Creek Rapid, one of the canyon's more challenging cataracts.

The next day, we cover what Mr. Bruchak says is "the biggest navigable water for a dory in North America." In 23 miles we navigate 16 named rapids that include several of the canyon's gnarliest.

Molten magma once dammed the Colorado, but the relentless river eroded away the impediment, leaving only a surging drop called Lava Falls in its wake. While not the most technically upsetting rapid, it's the one that drives more boatmen to hit the Maalox.

"Every time I make that turn and hear the roar, my heart jumps 15 beats faster," says Mr. Bruchak, with whom I ride today.

The cataract looks like a blender churning milkshakes in the river. We slowly approach the cataclysm as if we were condemned prisoners.

"Hang on," he says. "We're getting close. Get ready!"

We teeter at the brink, then swoop into the chaos. A ledge to the left has formed a gaping maw in the river. Mr. Bruchak pulls the dory to the edge of it, gaining momentum.

"Get ready! Big one!"

We sever a lateral wave and slice down to where two currents rush together to form a bulging V-wave. The bow rises. Water flies.

"Bigger one coming! Hang on! BIGGER ONE."

We plow through a second, larger V-wave. Torrents crash by the boat's bow. I grip the gunwales so tightly, I expect to leave indentations in the wood. We bound, bounce and bash through the rapid's gut, finally exiting through the tail waves.

Nine seconds after it began, it's over. Mr. Bruchak pulls into the eddy and everyone breathes a triumphant sigh of relief.

"There's no place on the river like that!" he exclaims.

I look at the bottom of the boat. Only 4 inches of water slosh in the foot well. Maybe Lava Falls isn't so bad after all.

Dan Leeth is a freelance writer in Colorado.

Dory trip operators

•Grand Canyon Dories (1-800-877-3679; www.oars.com) offers 15- to 19-day full-canyon trips. Rates: from $4,716, which includes all food and camping gear plus transfer from Flagstaff, Ariz. Shorter trips start at $2,615. Trips are available April through October.

•Grand Canyon Expeditions (1-800-544-2691; www.gcex.com).

Resources

•List of all raft-trip operators at Grand Canyon River Outfitters Association's Web site (www.gcroa.org ).

•National Park Service, 928-638-7888; www.nps.gov/grca.

•Arizona Office of Tourism, 1-866-275-5816; www.arizonaguide.com.