If it weren’t for the windblown ripples across the surface, I might have thought the lovely lake bed was empty—that is how clear the water was. It was as sparkly as glass just swiped clean, only there didn’t seem to be anything chemical-laden like glass cleaner to be found up at 10,000 feet. And that was exactly the point. Although the water was as frigid as it was pure—snow patches dotted the ground nearby—I scrambled in, put my head under, and even splashed about for a few minutes. Everything about my body seemed to contract with the cold, and I emerged feeling a welcome sense of renewal. I won’t go as far as to say it was a rebirth of the spiritual sort, but I did feel very, very clean, both inside and out.

I gravitate toward water. I live just blocks from the ocean, swim in an Olympic-size pool several times a week, and admit to being fond of long, ecologically incautious showers. But I’m also keenly aware that the water I swim and bathe in is far from ideal. Sometimes the city beach I frequent gets such a poor water-quality rating that I have to stay away for weeks. My morning workouts in the pool leave the scent of chlorine on my skin for the entire day, and the mineral-laden water that courses through our home pipes deposits a residue on the fixtures (and probably delivers other things I’d rather not know about). I’m not about to give up swimming, living by the beach, or taking showers, but it gives me great pleasure to know that I can also occasionally immerse myself in a body of pristine water, just as I did that day high up in Yosemite National Park. In fact, I’ve made it a kind of mission to search out and savor as many unspoiled little lakes, ponds, and swimming holes as I can.

If you listen to environmentalists and climate scientists, the state of water in this world is worrisome. What we hear about most these days is that global warming is melting the polar ice caps, causing our oceans and seas to rise to frighteningly high levels, but we’re also at risk for a worldwide water shortage, claims science writer Fred Pearce in his book When the Rivers Run Dry (Beacon Press, 2006). In fact, as Pearce explains, the two aren’t unrelated, making the world at risk for both floods and droughts. Pollution continues to be a problem, too. As the Natural Resources Defense Council, an environmental group, notes, some progress has been made in cleaning up oceans, lakes, and rivers, but much still needs to be done.

I must confess, though, that it’s easy to forget all of that when you’ve just jumped into a clear mountain lake or you’re hiking through a forest and come upon, much to your surprise, a perfect little swimming hole. I’m especially enamored of the latter, a passion I share with Pancho Doll, a man who has devoted the last nine years of his life to the discovery and documentation of these sometimes-hidden gems. “Swimming holes tend to reveal themselves so suddenly,” says Doll, author of the series Day Trips with a Splash (check out his Web site, www.running-water.com, to locate local swimming holes). “You’ll hear a creek, then all at once you’ll see a gorgeous pool of water just begging you to jump in.”

Doll became a swimming-hole aficionado by accident. After being laid off from his job as a reporter for the Los Angeles Times, he decided to take six months to see some of the natural wonders that native Californians are always talking about. A friend took him to a swimming hole near the Yuba River in Northern California, and that was it: He’d found his calling. All these years later, Doll is still traveling around in a well-appointed truck—most recently in the Pacific Northwest—hunting for little-known bodies of water, many of them off the beaten path. “Once you get there, you have a reasonable expectation of privacy,” says Doll. “Some are so remote that if someone shows up, you’re probably being followed.”

It should also be said that some swimming holes are well known, although that doesn’t make them any less alluring. One spring day, on the outskirts of Tucson, a friend guided me through an arid landscape of giant saguaros, century plants, and barrel cacti with the promise of a swimming hole ahead. It seemed the last place you’d expect to find water, least of all a swimming hole. However, a few miles into the canyon, the terrain changed to reveal not just one swimming hole, but several pools of varying depths and widths encased in slick rock. It seemed to be a popular destination: Many people were splashing about and sunning themselves on the surrounding rocks.

I ask Doll if he’s familiar with the place. Yes, he says, he’s covered the Southwest, too; it’s called Seven Falls. “Swimming holes in the Southwest are not an intuitive topic,” says Doll. “But while you may not expect to find any in the desert, there they are—these gorgeous tanks of water in the rock.” And to Doll’s mind, rock is the secret to a great swimming hole. “The best swimming holes are those where the rock has been eroded into a nice container.”

Personally, I’m not fussy about the architecture of my swimming holes. What I like in a swimming hole is distance—that is, I like it to be far enough away that it takes a good long hike to get there. That way I get in a workout and, once I get there, diving into the water seems like an even greater reward (all the more so if you’re hiking when the weather is unforgiving). One of my most memorable swimming-hole adventures took place on the first real torpid day of summer, the kind of day where the heat makes your hair lie flat and your clothes dampen and cling. We—adults, kids, and canines—had been hiking for about an hour and, while the trail wasn’t particularly arduous, we were wilting nonetheless. Even the dogs, who usually run ahead, seemed depleted. Finally, after we crossed a dry riverbed and ascended a small rise, we heard the familiar gurgle of a creek. Relief! Around the bend, willowy trees opened up to reveal a sizable pond, glittering green in the sunlight. Five minutes later I was backstroking across its cool length, gazing up at the hot blue sky.

My usual swims—in a pool with a Masters coach barking timed sets at me and my lane mates—are great exercise. Swimming, if you do it vigorously enough, improves your cardiovascular system without punishing your joints. And since just about every muscle comes into play as you swim, it builds strength throughout the body. I also like the meditative quality of swimming. As you stroke across the pool, you hear little but the splash of your own hands and feet as they break the water’s surface. It can be both calming and exhilarating. Pick up your pace or switch to an especially challenging stroke like the butterfly, and your heart will pound with accomplishment. Sometimes I use hand paddles, which cause resistance and make the arms work harder, or a kickboard, which allows you to isolate the muscles in your legs. To me, swimming in a pool is never a bore.

Still, sometimes I long to break free of the lane lines and swim languidly without pressure. How nice to turn my head and see trees or meadows instead of the walls of the aquatic complex. In the pool, I swim steadily and hard. In a swimming hole or pond, I swim in a dreamier, more playful, and less dutiful way. I breaststroke with my head above the water so I can better take in the scenery. I flip on my back and propel my body by moving my arms and legs as if I were making angels in the snow. If the hole is deep enough, I climb up on the rocks and jump in. I let the dogs chase me and the kids race me.

I came late to discovering these out-of-the-way little bodies of water. My family spent summers at the ocean, never venturing into the backcountry or woods where swimming holes, ponds, and mountain lakes are found. But I quickly fell in love with the first hidden pond I encountered: Fresh Pond on New York’s Shelter Island. The pond is tucked behind a thicket of trees—you wouldn’t know it’s there unless someone told you—and what a pond it is. It’s vast enough to do laps back and forth, and the last time I visited, there was a rope tied to a tree that let you swing over the water and drop in.

Since my initiation, I’ve dipped into swimming holes in places as far away as Hawaii and as near as two hours from home. Each place has its charms. At Ten-Foot Hole, outside the town of Ojai, California, it’s the wide expanse of water and the wraparound cliffs and trees that lend privacy. At Galena Creek, up in Mountain Home State Forest, Nevada, it’s the multiple little waterfalls that run down the sides of the polished rocks and into the pool, and the giant sequoia trees that loom around its edges. In Maui, there’s a spot called Waimoko Falls, which, besides being home to a 400-foot waterfall, is dotted with swimming holes. To get there, you must first hike through a bamboo grove with bamboo so thick and high that it barely lets in any light. Once you make your way through the grove (there’s a wooden plank path down its center so you can avoid the mud), you eventually come across several small pools. On the day I was there, the water was so high that we couldn’t walk on the rocks. Instead, we had to swim through some of the smaller pools (with our clothes on!) to get to our final destination, a larger, deeper pool fed by a vigorous waterfall. Standing at the top of a cliff about 12 feet high, I tried to forget my fear of heights, closed my eyes, and leapt in.

Lately I’ve been thinking that there might be other good ways to enjoy these isolated pockets of water. While hiking near mountain lakes, I’ve seen people kayaking, only to wonder how they got a boat up to 8,000 feet when the parking lot is down at 4,000. The secret is portable kayaks, some of which are inflatable. Still, you need to be a very motivated paddler, since even the lightest boats are close to 17 pounds (not including paddles). But how wonderful to be skimming across high-altitude freshwater with nothing but the surrounding mountains to distract you.

That was kind of the idea Harry Patterson and his friends had when they decided to windsurf across Canadian lakes. Given that they’re miles across, the lakes aren’t your typical backcountry puddles, but at several thousand feet above sea level, they’re still fairly far from the madding crowd. What enticed the intrepid Patterson to set his sailboard into Lake Minnewanka near Banff in Alberta was the wind. “It’s really, really gusty and really, really cold,” says the Banff-based anesthesiologist. “It’s not Hawaii, but there are also no sharks.” Patterson has also windsurfed Columbia Lake in British Columbia. That lake, too, is icy, if somewhat less so. However, that cold is part of what makes it fun. “After a couple of trips across the lake, it feels great to get out and warm up in the sun,” says Patterson.

Hmmm. Maybe I will stick to ponds and swimming holes after all. They’re a bit easier, a little more calming. Perhaps the expert, Pancho Doll, explains it best: “There’s always moving water, noise, and motion leading up to a swimming hole, then when you get to the pool, it’s like the weekend. All the tension relaxes and it literally and metaphorically becomes reflective.”

When the weather is too cold for seeking water, I often look at two pictures torn from magazines that are tacked on the wall above my desk. One is an illustration of a man doing a back dive into a swimming hole surrounded by rocky cliffs. The other, which I especially love, is a photograph of two people at a marshy pond. One of them is perched on a raft while the other is dangling over the water, her hands clutching the seat of a swing. In my mind, that’s me, poised to drop in.

Daryn Eller, who swims for fun and fitness, lives in Venice, California.