One of my favorite parts of a plane ride is the descent. While my fellow passengers close their eyes and brace for the drop, I’m glued to the window, trying to identify the town’s features from my bird’s-eye view. The drab brown parcels confuse me, as do the green squares (is that a park or cropland?). But the easiest areas to spot are the affluent neighborhoods, with perfect rectangles of aqua water dotting the landscape. They seem intended for only one thing: wet refreshment. But if Mick Hilleary and his colleagues have their way, the purpose of a backyard pool may not be so clear-cut. And it might even be harder to spot from Seat 4A.

Hilleary is one of a handful of designers who build natural swimming pools — recreational structures that combine the clear water of a traditional pool with the lush, untamed scenery of a wilderness pond. Cleaned without the aid of harsh chemicals, the ponds are slowly garnering attention in the U.S. as homeowners seek healthier, more attractive alternatives for water recreation.

“Sometimes we get couples,” says Hilleary, owner of Total Habitat, a firm based in Bonner Springs, Kans., that builds pools and zoo exhibits. “One partner wants a pool, one wants a pond. When they see our thing, it saves the marriage.”

The most notable feature of a natural swimming pool is its lack of chlorine, a substance which some say causes skin irritation and aggravates pre-existing health conditions. A 2002 study published in Occupational and Environmental Medicine found that children who swam regularly in chlorinated pools had a higher risk for developing asthma. Natural pools also don’t require emptying and refilling like many chlorine pools, says Michael Littlewood, a landscape artist and natural-pool designer who wrote Natural Swimming Pools: Inspiration for Harmony with Nature (Schiffer, 2005).

Natural swimming pools can vary widely in appearance, from a simple geometric shape to structures that are more complex, complete with decks and bridges. But essential to each of them is a regeneration zone — an area that serves to keep the water clean. Pumps and skimmers remove debris and keep the water from becoming stagnant, while gravel beds and fast-growing aquatic plants absorb and filter out pollutants and bacteria. The result: a miniature, man-made ecosystem that’s just as safe to swim in as the “sterile, dead water” of a chlorine pool, says Bryan Morse, owner of Expanding Horizons, a company in Vista, Calif., that builds rock-and-water projects.

Some people are turned off by the algae that can cling in small amounts to the walls of a natural swimming pool in the hotter months, Morse adds. “They assume it’s dirty,” he says. “But algae is not dirty or dangerous to humans. It’s just another plant.”

Though a novelty in the U.S., natural pools have been around for at least 15 years in Europe. David Nettleton, owner of Bristol, England–based pool company Clear Water Revival, attributed their stateside scarcity to the relative lack of working prototypes here. “If you get more examples in the U.S., that would really kick it off,” Nettleton says. 

The infrastructure to support owners of natural swimming pools — like companies that build them, or supply materials for them — is also lacking, Hilleary says. His company has long-range plans to train builders to construct natural pools and to work with suppliers so the materials will be more readily available. Hilleary and Littlewood have formed a trade group, the Natural Swimming Pool Association, to set standards for the industry. The group currently consists of only a handful of members, but Hilleary says others are preparing to come on board soon.

The cost of installing a natural swimming pool is comparable with that of a regular in-ground pool, though a natural pool’s relative rarity may drive prices up a bit, Nettleton says. “Regular swimming pools are a bit more standard in their design. We don’t have, as yet, a range of off-the-shelf options for natural swimming pools.” Many owners also like to enhance their pools with elaborate landscaping and boulders, Hilleary says, which further increases cost. Littlewood estimates a ballpark cost of a natural swimming pool at about $900 per square yard, a figure that’s based mostly on European projects, he says.

Most designers agree, however, that a natural pool’s self-sustaining ecosystem results in a different (and often less frequent) maintenance schedule for the owner once established. Usually all that’s required is an annual trimming of vegetation and the occasional use of a pool vacuum to remove excess sediment, Littlewood says. Morse, who lives in Vista, Calif., built his own pool in 2001 out of a backyard pond. He says he spends very little time keeping it up, though he does plan to recolor the light-aqua cement liner to dark gray to make the water look bluer, creating a “lagoon-in-a-tropical-location kind of effect,” he says.

Natural swimming pools can be installed in just about any region of the U.S., but it’s crucial to adapt the design to the local climate. Some aquatic plants can choke out other vegetation, while other species may not grow vigorously enough if the climate is too cold. Water hyacinths, for example, which tend to be invasive, will take over a pool in Florida, but they usually do well in San Diego, Morse says. Littlewood’s book includes an index of plants appropriate for each region of the U.S. 

The pool’s depth should also be appropriate for local weather; owners in warm climates should have theirs dug about 10 feet deep, Littlewood says, to keep the water from becoming too warm and encouraging algae growth.

The best feature of a natural swimming pool is its versatility, Hilleary says. “You can enjoy them all year round,” he says. “I have clients sending me e-mails that they had breakfast by their pool because it was a nice December morning. They never remember doing that around their traditional pool. We have type-A workaholics spending every night by the pond. The therapy is through the roof.”

Story by Jennifer Acosta Scott. This article originally appeared in Plenty in August 2007. The story was added to in June 2009.

Copyright Environ Press 2007.