Wading into Chocorua Lake, I cast a glance at the lightening sky, then dip my hand into the cool, clear water and make the sign of the cross. Just before 7 a.m. the lake is gray and quiet, a thin layer of mist skating over the surface. There’s no one around, not even a car passing on Route 16, when I lower my goggles and strike off for the western shore, a half-mile distant.

Simply by exercising a little Yankee ingenuity, the no-frills traveler can put together a vigorous itinerary that takes advantage of rugged New England attractions. When I was a kid growing up in Methuen, Mass., my friends and I would ride our bikes several miles up the railroad bed into Salem, N.H., fish the Spicket River all morning, cruise back to hold an impromptu tennis tournament on the public courts, and then swim across Forest Lake in the afternoon. In this era of overpriced vacations, I decided to pay homage to those do-it-yourself adventures by creating what I call the "homemade upcountry triathlon." Here in the White Mountains near Conway, NH, I intend to swim a mile, go rock climbing on Whitehorse Ledge, and finish up with a mountain bike ride along the Swift River—all in a single day.

Staring into the depths as I swim, I watch the lake change from gray to greenish brown as the sun rises over my left shoulder. For a long while all I can hear is my own breathing and then the raucous giggle of a loon comes across the lake, startling me. Ten minutes from shore, I poke my head up to see the rocky dome of Mount Chocorua looming out of the mist.

Nearing the far bank, I stagger to my feet and attempt to get my bearings. The state forest comes right to the water's edge, the trees so dense along shore that the morning sun doesn't penetrate very far, giving the landscape a spooky aspect. When I turn around, I realize that I've taken a diagonal course and will have to slog back over a longer distance than I anticipated, probably a mile and a half when I finally reemerge at my starting point 45 minutes later.

It's still early and I feel pretty fresh but I am already concerned about the extra effort I've used on the swim. I quickly skin off my wetsuit, toss my bag in the car and roar off toward Whitehorse Ledge, 30 minutes north. This is the ultimate pocket odyssey, a slice of hard living on the cheap. The key to it all is planning: trail mix and tri-suit, mountain bike and medical kit, and a cooler filled with sandwiches, fruit, and energy drinks. There are no aid stations at the homemade triathlon.

By mid-morning, I've been fitted with a climbing harness, helmet, and "rock shoes," and am standing at the base of Whitehorse with Al Hospers, a guide with the International Mountain Climbing School in North Conway. I have zero experience with technical climbing.

Hospers, 62, a lean, craggy faced man with sandy hair, is one of those rough-hewn Renaissance characters you'll find scattered across the high country. In 1971, he earned his degree in sculpture from the University of Florida. He later toured as the bass player for Blood, Sweat & Tears, and was an early hire at the video game company that developed Guitar Hero. Savvy investments allowed him to drop out of the 9-to-5 and now he climbs 150 days a year, on rock and ice.

"Retirement used to be playing cards and drinking martinis," says Hospers. "I can't imagine what that's like."

Whitehorse Ledge and neighboring Cathedral Ledge form one of the premier rock climbing venues in New England. Above me, the undulating face of the slab rises vertically for over 700 feet until it's broken up by jutting boulders and a toupee of scrub pines. Hospers has chosen a route called "Sea of Holes," which is marked with divots, dents, and vertical cracks, or "flakes." As he goes over the belay system we'll be using to stay roped to the cliff, my gaze strays upward to the mostly smooth rock. The sky is clear and nearly cloudless, temperatures already in the 80s. From this angle, it looks like a hell of a climb.

The plan is to ascend three of the four "pitches" on this route, approximately 180 feet each, and then to rappel back down. Leading the way, Hospers scrambles up the first pitch like he has suction cups on his feet, maintaining a steady commentary as he goes: practical instruction, bits of climbing arcana, and the prehistoric narrative of the glacier that carved out the obstacle we are currently engaged upon.

"My wife says I yak a lot," Hospers says.

Soon I'm following him up the pitch. My hands searching for dimples in the rock, I move steadily onward in my grippy shoes, learning to "trust my feet" as I've been told. In minutes, I reach the first anchor, where Hospers is suspended by a "sling" that's clipped into a steel bolt driven into the rock. Again he goes ahead, installing the "protection"—bits of hardware inserted into tiny crevices to provide additional security if he should slip and fall.

The next two pitches are steeper, eating up more of my time and energy. But just as Hospers predicted, every tiny feature of the rock appears magnified: the next handhold, the best foot placement. I can see each fleck of mica, the scribbles of lichen and moss, even an ant traversing the cliff just inches from my nose. It's like hearing a foreign language for the first time and being surprised when you find yourself understanding it.

More than two hours in, Hospers and I are slung into the third anchor 550 feet above the ground. He notes the time, asking if I want to go on to the final anchor, located up and over a jagged ridge suspended above us. I swig from my water bottle, squint upward, and say, "Let's go for it." But no sooner has Hospers ascended to the top, when I begin to regret my decision. The sun is beating down on me and it takes 15 minutes to climb the next 10 feet, my chest heaving as I pause for breath, hugging the sheer cliff. Hospers calls down to ask if I'm all right. I can hardly speak, and twice wave my hands in front of my face in the international sign for "no mas."

Hospers lowers me back to the third anchor and unhitches himself from the sling and rappels down to me. When I flub an easy question about the ropes, he looks at me steadily and says, "You're tired. We're going down." No argument from me.

We descend two pitches side by side, then Hospers continues to the ground and I rappel down the last pitch. Fifteen minutes later, we're lounging in the shade. "I bet you learned something about yourself today," Hospers says. "Yeah, don't swim a mile and a half when you plan to swim a mile," I reply.

By 4 p.m., I'm back in my car heading for the Kancamagus when an old Rod Stewart song comes over the radio:

Take me back, carry me back
Down to Gasoline Alley where I started from

As a boy, my family vacations were spent fishing and hiking along the Swift River, so I've decided to bike the Lower Nanamocomuck ski trail, which runs west from the Albany Covered Bridge to Rocky Gorge. At the bridge, I rig up my bike and set off. It's cool beneath the trees and I pedal along at a smooth clip, the Swift running noisily to my left.

My quads are the only muscle group that isn't fatigued and cycling the final leg is starting to look like a stroke of genius. But after five minutes of easy riding, the trail narrows to an overgrown rutted ditch, veers into a stretch of tangled forest, and climbs a series of steep, rocky hills. After dismounting repeatedly to shoulder the bike over felled trees and around swamps, I begin to wonder why I didn't choose kayaking instead.

An hour later, scratched, muddy, and soaked in sweat, I ride down from the tree line, cross the footbridge over the gorge and find my way out to the Kancamagus. Riding on the shoulder of the Kanc is probably the most dangerous thing I've done all day, but it's a nice downhill grade and the steady breeze against my skin cheers me up considerably. Very few cars pass me enroute, and I'm free to mull over the day's events. I've covered nearly a mile and a half on my swim, 550 vertical feet on Whitehorse Ledge, and 12 miles on the bike in five hours. I'm pretty darned tired, but happy nonetheless. Flying along the Kanc, all I want from life right now is a dunk in the Swift and a cold beer.

Jay Atkinson is the author, most recently, of Paradise Road: Jack Kerouac's Lost Highway and My Search for America. He teaches journalism at Boston University.