I have a vivid childhood memory of emerging from our local swimming pool with stinging red eyes and bleach-blonde hair tips, smelling so strongly of chlorine that our dog would refuse to greet me until after I’d showered. Back then, I thought that chemical smell meant “clean”—the stronger the better. Shows how much I knew. It wasn’t until many years later, standing at the edge of what looked like an impossibly clear natural pond in Austria, watching people gleefully splash around in water purified entirely by plants and microorganisms, that I realized there was another way.
“You can actually swim in that?” I asked my host, convinced there must be some hidden filtration system pumping chemicals into the water.
“Of course,” she laughed. “We swim here every day in summer. No chemicals, just plants doing what they naturally do.”
I tentatively dipped my toes in, half-expecting them to emerge covered in slime. Instead, the water was cool, crystal clear, and felt impossibly soft against my skin. By the end of that visit, I was fully converted to the church of natural swimming pools and determined to learn everything about how these magical-seeming systems worked.
That Austrian pool, I later learned, was part of a movement that began in the 1980s when several European designers and ecologists started experimenting with using constructed wetlands to purify swimming water. The concept was radically simple: harness the same biological processes that keep natural lakes and ponds clean, but optimize them for swimming use. No chlorine, no bromine, no algaecides or other chemicals—just a carefully designed ecosystem doing what nature has perfected over millions of years.
After returning to the UK, I became slightly obsessed. I visited every natural swimming pool I could find, interviewed designers and owners, and even enrolled in a short course on aquatic plant systems. What I discovered was both incredibly simple in concept and fascinatingly complex in its ecological details.
The fundamental principle behind natural swimming pools is biological filtration. Unlike conventional pools that rely on chemicals to kill bacteria and prevent algae growth, natural pools use living systems—plants, beneficial bacteria, and other microorganisms—to maintain water quality. It’s the same process that keeps natural bodies of water clean, just engineered to work more efficiently in a controlled environment.
Most natural swimming pools are divided into two zones: a swimming area and a regeneration zone (sometimes called the filtration zone). The swimming area is what you’d expect—deeper water kept clear of plants for unobstructed swimming. The regeneration zone is the biological engine of the system—a planted area with carefully selected aquatic plants growing in specialized substrates that host the microorganisms that do the actual water purification.
Water circulates between these zones either passively through clever hydraulic design or with the assistance of small, energy-efficient pumps. As it passes through the regeneration zone, the plants and microorganisms remove nutrients, filter out particulates, and create an environment hostile to harmful bacteria. The result is water that’s clean and safe for swimming without a single chemical added.
My friend Sasha, who’s built several natural pools through her landscape design business, explains it using a nutrient competition model: “Harmful bacteria need nutrients to thrive. So do plants. In a well-designed natural pool, the plants and beneficial microorganisms are better at grabbing those nutrients, essentially starving out the harmful bacteria.” It’s ecological warfare at a microscopic level, and when designed properly, the good guys always win.
The first time I saw one being built, I was surprised by the technical sophistication hidden beneath what looks like a naturalistic water feature. There are specialized growing media, carefully calculated flow rates, specific plant selections based on local conditions, and various forms of biological filtration working in concert. It’s proper ecological engineering, not just “dig a hole and add water and plants” as I’d naively imagined.
The swimming zone typically has an impermeable liner (usually EPDM rubber, PVC, or reinforced polypropylene) and can be finished in various ways to resemble anything from a conventional pool to a natural pond. Some have wooden, stone, or concrete edges; others feature gently sloping naturalistic edges that blur the boundary between water and land. The aesthetic flexibility is one of the system’s most appealing aspects—natural pools can be designed to complement any landscape from formal to wildly naturalistic.
The regeneration zone is where the magic happens. It consists of carefully selected aquatic plants growing in specialized substrate that provides ideal habitat for the biofilm—that’s the community of beneficial bacteria and other microorganisms that do much of the water purification work. Common plants include water lilies, rushes, irises, and underwater oxygenators like hornwort, though the specific selection varies based on climate and water conditions.
What surprised me most when I started researching these systems was the remarkable water quality they achieve. Studies have shown that properly designed natural pools consistently meet or exceed public health standards for recreational waters. The crystal clear water isn’t just visually appealing—it’s genuinely clean from a microbiological perspective.
My colleague Jamie had his water independently tested after installing a natural pool at his home in Devon. “The lab actually called me to double-check what kind of water body they were testing,” he told me, “because the results showed fewer harmful bacteria than most conventional pools they test. They couldn’t believe it was achieved without chemicals.”
Of course, like any ecological system, natural pools require a balance. Too many nutrients (often from pollen, leaves, or swimmer contaminants like sunscreen) can throw things off and potentially lead to algae issues. But a well-designed system includes multiple layers of defense—from physical filtration to plant uptake to microbial competition—creating a robust, resilient purification process.
The environmental benefits compared to conventional pools are substantial. No harmful chemicals being produced, transported, stored, or eventually released into the environment. Significantly lower energy use, particularly compared to heated conventional pools. And the creation of valuable habitat for insects, amphibians, and birds—turning what would be an ecological dead zone into a biodiversity hotspot.
After years of writing about them, I finally got my chance to be directly involved in creating one when my local community garden was looking to redevelop an unused section of their property. I somewhat rashly suggested a small natural swimming pond that could double as an educational feature about aquatic ecosystems. To my surprise (and mild terror), they loved the idea.
What followed was a crash course in the practical realities of natural pool creation. Our first design meeting involved five enthusiastic gardeners, two skeptical board members, and me with a stack of books and articles but no actual construction experience. Thankfully, we found a designer who specialized in natural pools and was willing to work with our limited budget and volunteer labor force.
The excavation weekend was equal parts exhausting and exhilarating. Twenty volunteers with shovels, wheelbarrows, and extraordinary optimism, moving several tons of earth to create the distinct swimming and regeneration zones. I still have the blister scars. The moment when we laid the last section of liner and started filling the pool remains one of my favorite memories—watching the abstract idea I’d championed slowly take physical form.
The planting was a community affair too. We sourced native species from a specialized aquatic nursery and spent a day carefully positioning each plant according to our designer’s detailed plan. Water mint and marsh marigold at the pond margins. Yellow flag iris and flowering rush in the shallows. Submerged oxygenators like hornwort and water milfoil in the deeper areas of the regeneration zone. Each species had a specific role in the filtration system, from nutrient uptake to providing habitat for beneficial microorganisms.
We made plenty of mistakes along the way. Our first pump was undersized, leading to poor circulation and some early algae issues. We underestimated the impact of falling leaves from nearby trees and had to install a more robust skimmer system. And we learned the hard way about the importance of proper edge design when heavy rains caused significant soil erosion into the pool during the first winter.
But the system proved remarkably forgiving of our amateur efforts. Within about three months of completion, the natural processes kicked in properly, and the water cleared to a beautiful crystal blue. The first community swim day was a proper revelation for many locals who’d never experienced anything but chlorinated pools. The same questions kept coming up: “There really aren’t any chemicals?” “Why doesn’t it smell?” “How is it so clear?” Explaining the biological processes at work became my standard poolside conversation.
Three years on, our community natural pool has become the unexpected heart of the garden. Children splash at the shallow edges while learning about aquatic insects and plant life. Older visitors enjoy peaceful swims surrounded by dragonflies and the occasional visiting frog. The regeneration zone has bloomed into a stunning display of aquatic plants that change with the seasons. Even in winter, when swimming is only for the brave (or foolish—I’ll admit to a few midwinter dips that left me questioning my life choices), the pool remains a beautiful, ecologically rich feature.
The maintenance has proven less intensive than many feared. We have a monthly volunteer session during the swimming season to check water levels, clean the small pump filter, remove any debris, and manage the plants as needed. The system uses about 70% less electricity than a comparable conventional pool would require, and of course, there are no ongoing chemical costs.
For those interested in creating their own natural swimming pool, there are several approaches with varying levels of intervention and naturalism. On one end of the spectrum are highly engineered systems with distinct formal swimming areas and separate planted filtration zones—these can look quite similar to conventional pools but operate on biological principles. On the other end are naturalistic designs that resemble wild ponds but include carefully designed elements to maintain water quality suitable for swimming.
The cost varies widely depending on size, design complexity, and how much DIY work you’re willing to tackle. A professionally installed natural pool typically costs about the same as a high-end conventional pool initially, but the operational costs are substantially lower over time. No chemicals to buy, less energy consumption, and simpler maintenance requirements add up to significant savings across the pool’s lifetime.
Climate considerations matter too. In the UK’s temperate climate, natural pools work brilliantly with minimal heating requirements (though some people do add solar heating to extend the comfortable swimming season). In very hot climates, larger regeneration zones might be needed to handle increased biological activity. In cold regions, the system goes dormant in winter but readily reactivates when temperatures warm in spring.
I’ve now swum in dozens of natural pools across Europe, from tiny backyard installations to large community facilities. Each has its own character and quirks, but all share that remarkable water quality that has to be experienced to be believed. There’s something profoundly different about swimming in living water—it feels softer against the skin, has no chemical smell, and creates a connection to natural processes that conventional pools simply can’t match.
Of course, natural pools aren’t for everyone. If you want guaranteed 29°C water year-round or can’t tolerate the occasional water beetle or dragonfly larva, you might prefer a conventional pool. The water clarity, while excellent, can vary slightly with weather conditions and seasons in a way that chemically controlled pools don’t. And while maintenance is generally simpler, it does require a basic understanding of the ecological balance rather than just following a chemical testing and dosing regimen.
But for those willing to work with natural processes rather than against them, a natural swimming pool offers a remarkable alternative to chemical-dependent systems. It transforms what would typically be an ecological dead zone—a conventional chlorinated pool—into a thriving habitat that provides joy for swimmers and wildlife alike.
Our community pool has become my favorite example of how ecological thinking can enhance rather than diminish human pleasure. Visitors consistently comment that swimming feels better—no stinging eyes, no chemical smell, no dry skin afterward. The diverse plant life and the wildlife it attracts create a multi-sensory experience that sterile conventional pools can’t match. And there’s a certain satisfaction in floating on your back, watching dragonflies hover above water lilies, knowing that the system cleaning the water around you is the same one that’s been perfecting itself in natural lakes and ponds for millions of years.
Modern life offers vanishingly few opportunities to directly experience the brilliance of natural systems working as they should. A natural swimming pool creates exactly that opportunity, right in your garden or community space—a daily reminder that working with nature rather than against it often yields the most elegant solutions to our needs. Now if you’ll excuse me, it’s a surprisingly warm spring day, and there’s a dragonfly-patrolled pool calling my name.
