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Havasu Falls, Supai, Arizona
This shocking Caribbean-blue pool—on the bottom of the Grand Canyon near the Native American community of Supai—is for the most tenacious of swimming-hole devotees. There are only three ways to get to Havasu Falls: hire a helicopter, hike 10 miles, or ride a pack mule. Plus, you'll need to purchase an entry permit, and, unless you're a hardcore trail runner, book a night at the Havasupai Lodge or campsite. But it's so worth it. Pancho Doll, who wrote two books on America's swimming holes, calls it the best in the world. After a long desert trek, even the mist from the 120-foot cascade is refreshing. Swimming behind the torrential falls or floating on your back and taking in the view is the real reward.
What's Nearby: Supai has a small grocery store and cafe. It's also one of two places in the country where U.S. mail is delivered by mules.
Sliding Rock, Pisgah National Forest, North Carolina
Break out your old cutoff jeans shorts for this 60-foot natural waterslide just off the Blue Ridge Parkway near Asheville. Each minute 11,000 gallons of water pour over a huge, mostly smooth boulder and into a seven-foot plunge pool. If the ride doesn't take your breath away, the water temperature will. The cool mountain stream that powers this Sliding Rock ride is only about 50 to 60 degrees in summer. Sliders of all ages shriek, grimace, and tiptoe through it but come back for more, even when long lines snake down the entire rock face. Lifeguards supervise in summer, and small kids can ride in an adult's lap.
What's Nearby: To see an authentic slice of Appalachia, check out Brevard, which was named one of America's Coolest Small Towns by Budget Travel magazine in 2010. The woods and waterfalls of DuPont State Recreational Forest were the film set for the arena in The Hunger Games.
Hamilton Pool Nature Preserve, Dripping Springs, Texas
When summer temps hit 100, Austinites have plenty of great swimming holes to choose from, including Barton Springs right in the middle of town. But the legendary get-away-from-it-all spot is Hamilton Pool Nature Preserve, about 25 miles west of Austin off Highway 71. A quarter-mile trail descends to the canyon pool. Rimming one edge of the clear blue-green waters are a limestone grotto and a 50-foot waterfall; here you can play in the shower or find a shady seat on the rocks beneath its overhang. At the other end is a sunny beach. On summer weekends, when the 75-vehicle parking lot reaches capacity, preserve officials manage the one-in, one-out system, which is not such a bad thing once you're in.
What's Nearby: Preserve trails lead to scenic areas along the Pedernales River. At Pace Bend Park on Lake Travis, swimming and boating are popular.
Diana's Baths, Bartlett, New Hampshire
Once the location of a sawmill operation and now a protected historical site in the White Mountain National Forest, the Diana's Baths swimming hole is best on a warm, full-moon night. Locals say it's the most romantic spot in Mt. Washington Valley: secluded, private, and perfect for skinny-dipping under the stars. By day, the cascading falls and pools, waterspouts, and granite basins are a family favorite. An easy half-mile trail leads from the parking area to Diana's Baths just past Echo Lake State Park near North Conway.
What's Nearby: A drive to the top of the park's Cathedral Ledge reveals a great view of the valley. The ledge is also a popular rock-climbing area. Take the kids on a Conway Scenic Railroad train ride or to the sandy beach at Echo Lake.
Lower Calf Creek Falls, Grand Staircase-Escalante National Monument, Utah
It's a parched land, Utah's Grand Staircase-Escalante National Monument. But the 126-foot Lower Calf Creek Falls are miraculously resilient, with a year-round flow into a lush oasis and pool. Set out early to beat the desert sun on the five-and-a-half mile round-trip trail. The loop, which starts at the Calf Creek Campground, cuts through a deep canyon and past Anasazi pictographs before coming to the falls. Here the water tumbles down and drenches the mineral-streaked Navajo Sandstone walls that surround a swimming hole too clear, cool, and inviting to pass up.
What's Nearby: See the monument area's sculptured slickrock and hoodoos at Devil's Garden or the petrified wood at Escalante Petrified Forest State Park. In the town of Escalante, grab an outdoor seat at Kiva Koffeehouse and take in the incredible view.
Whiteoak Canyon, Shenandoah National Park, Virginia
For swimming-hole enthusiasts who think one is never enough, there's Whiteoak Canyon in Shenandoah National Park, 75 miles from Washington, D.C. Here, just off of Skyline Drive, you can go pool-hopping at the base of six different waterfalls that are linked by steep, rocky trails that wind throughout the canyon. Check out the trail map and envision working up a sweat on treks between plunges. The Upper Falls is the canyon's highest waterfall, but the huge pool at Cedar Run Falls makes a better end-of-day finale, with rocky ledges for jumping and, depending on the water level, a natural waterslide.
What's Nearby: In the park you can go trout fishing or arrange a guided trail ride on horseback. Explore heritage sites, including battlefields, presidential homes, and historical landmarks, on the Journey Through Hallowed Ground, a National Heritage Area along Route 15.
Baker's Bridge/Animas River, Durango, Colorado
In the 1969 film Butch Cassidy and the Sundance Kid 's famous jump scene, bank robbers on the lam, played by Paul Newman and Robert Redford, make a death-defying leap into a steep river gorge. The jump was filmed on the Animas River in Durango, just upstream from a popular local jump spot: Baker's Bridge, off Highway 550. For kids who grow up in the area, a bridge jump is a ceremonial rite of passage. The crazy feat requires channeling the tough-guy nerve of old Western movies. Jumpers wait for calm waters on summer days and usually show up in old shoes to show off with backflips.
What's Nearby: Go whitewater rafting on the Animas River or warm up with a soak at Trimble Hot Springs. Durango is also a popular mountain-and road-biking destination with its great trail systems and events.
Enfield Falls, Robert H. Treman State Park, New York
As this New York college town's popular green T-shirts proclaim, "Ithaca is Gorges." No doubt the landscape is stunning, but it also creates a picture-perfect backdrop for swimming holes. There are about 150 waterfalls within 10 miles of downtown, and Robert H. Treman State Park's Enfield Falls are a favorite among locals and undergrads. You can swim up and sit under a billowy curtain of water or soar from the cliffside diving board. Relax on a grassy patch or hike park trails to see 12 waterfalls, including the 115-foot Lucifer Falls.
What's Nearby: The parking pass ($7 per carload) is valid all day at three Ithaca state parks: Treman, Buttermilk Falls (with waterfall swimming and gorge hiking), and Taughannock Falls (three stories taller than Niagara). There are more than 100 wineries in the Finger Lakes region. For food lovers Ithaca boasts more restaurants per capita than New York City.
Johnson's Shut-Ins, Johnson's Shut-Ins State Park, Missouri
A two-hour drive south of St. Louis, the East Fork of the Black River swirls around giant volcanic chunks at Johnson's Shut-Ins State Park, Missouri's favorite natural water park. You can scramble over the rocks, slip and slide through the chutes, and relax in your own private pool (or "shut-in"). Finding your footing can be tricky, so water shoes are a must. The hike to the shut-ins is only a quarter-mile, and non-swimmers in your group can watch from the observation deck.
What's Nearby: The popular Taum Sauk section of the 360-mile Ozark Trail runs through Johnson's Shut-Ins State Park. In Lesterville you can take a Black River float trip in a canoe, raft, kayak, or inner tube. Elephant Rocks State Park is only 15 miles from the shut-ins.
Firehole River Canyon, Yellowstone National Park, Wyoming
In Yellowstone National Park all of the geysers and hot springs fall under the look-but-don't-touch rule. But this warm swimming hole, fed by distant thermal features, is one of only two spots in the park where you're allowed to take a dip. Near the park's western entrance, the Firehole River Canyon pool hits the spot after a long day of summertime sightseeing. Adventurous swimmers like to work their way upstream a bit before jumping into the rapids for a ride through the canyon. The main pool is shallower and better for younger kids.
What's Nearby: Old Faithful is a short drive south along the main park road. The uncrowded, one-way Firehole Canyon Drive takes you past 800-foot-thick lava flows and the 40-foot-high Firehole Falls. You can camp at Madison campground near the West Yellowstone entrance.
See slideshow: America's Best Swimming Holes