A GRAND CANYON OAR TRIP usually involves 16 passengers who ride in four boats and are served by a crew of six. If it's an expedition run by Grand Canyon Dories, each guide rows an elegant 17-foot dory named after a natural wonder that was heedlessly destroyed by man—in the case of the trip we're currently on, the Ticaboo, the Yampa, the Lava Cliff, and the Vale of Rhonda.

Every trip is also supported by two inflatable rafts that boast absolutely none of the dories' seductiveness or charm. These baggage boats haul most of the gear, grub, garbage, and goop, and they're assigned names that are considerably less lyrical. The first raft, the kitchen boat, carries a tangled assortment of tables, coolers, propane tanks, rescue gear, and watertight bags containing the clients' clothing. It's usually called the Mule, Ox, or Clydesdale. The other boat, my boat, is called the Jackass.

The toilet setup aboard the Jackass relies on the classic "20-mil" ammunition can, a narrow metal box—14.5 inches high, 18 inches long, and 8 inches wide—originally designed to store antitank grenade rockets for the army's M1A1 bazooka. Each "rocket box" can handle approximately 50 deposits of human waste and tips the scales at about 45 pounds when full. Its key feature is a rectangular lid that creates a watertight seal to prevent spillage while locking in the odors (well, most of them). When the lid is popped open, an aluminum flange called a riser is placed on top of the box and a toilet seat is mounted on the riser. During an early river trip back in the 1970s, shortly after this system was developed, the toilet seat was accidentally left behind, the rims of the riser left telltale indentations on everyone's bums, and the box got a nickname: the groover. (Some guides also call it the duker or the unit.)

Every evening when we pull into camp, the passengers clamber out of the dories and form a "fire line" at the bow of the Mule to help Monte unload the kitchen boat. Then everyone gets out of the way while I heave the toilet components onto the front deck of the Jackass and, with help from a guide, lug everything to a private spot, screened by trees or rocks, away from camp. I pull the lid off the box, slap on the seat, and declare the unit open for business.

Groover etiquette follows a strict protocol that the trip leader lays out in a "poo talk" on the expedition's first night. The most dismaying moment comes when it's revealed that the rocket box is used exclusively for solid waste, while urine goes into a special five-gallon bucket placed nearby. (If everyone peed in the groover, all my rocket boxes would be full before we got halfway to Lake Mead.)

Many passengers are initially appalled by this. Here they are, each having paid $4,314 for a deluxe river experience, only to discover that their daily constitutional requires a pants-around-the-ankles shuffle between a turd box and a pee bucket shared by 21 other people. But once they get their minds around it, the clients usually come to see the unit in a radically different light. It's not affection, exactly, but you could call it grateful acceptance.

Professional poo-men help things along with an eye for aesthetics. Over the years, every camp in the canyon has acquired an established groovering spot, and many of these locations are so sublime that they've become famous in their own right. At Whitmore Camp (186 miles from Lees Ferry), we like to set up under an overhanging chunk of black lava in a spot bathed in the scent of verbena blossoms. At a place called Ledges (mile 152), you have to climb 30 feet up a stone terrace and balance on a shelf of exquisitely sculpted Muav limestone. And at mile 136, you can sit on the thunder throne while staring into the center of Deer Creek Falls, the longest and loveliest cascade on the river.

Perched on the seat, it's not unusual for passengers to take notice of things they missed during the day's excitement: the trill of a canyon wren, the sweetest-sounding bird on the river, or the whorled mysteries of sunbeams playing among the interlocking currents of an eddy. "I've had passengers repeatedly tell me that groovering spots are some of the most exquisite places they've been," says Michael Ghiglieri, another guide I work with. "The pooper is often the place for meditation—so much so that people sometimes forget why they're sitting on the thing in the first place."

We toilet wranglers take pride in our skills, and I'm pleased to report that our talents have received modest recognition. In 1997, a guide named Joe Lindsay put together a book-length homage to the trials of poo-boating called Up Shit Creek: A Collection of Horrifyingly True Wilderness Toilet Misadventures. In 2002, a part-time poo captain named Scott Phair—a former pig farmer from Maine who now works as a high school principal—produced a calendar called "Groovin' in Grand Canyon," which featured photographs of the finest latrine venues on the river. At the time, Phair's finances permitted him to print only about 20 copies of this landmark publishing sensation. But he's hoping his next trip through the canyon, this spring, will yield material for a more commercially ambitious redux version, due out sometime in 2009.