One Saturday morning in April this year a group of swimmers assembled on the bank of Kinder Reservoir in Derbyshire and slipped into the icy pond. Signs reading “Danger Deep Water” and “Keep Out” surround the reservoir, which is operated by United Facilities, yet the 18 people were untroubled by the warnings. They had signs too, handmade placards held aloft as they bobbed together. “The Right To Swim”, read one.

To an observer, one head will have stood out among the party. Owen Hayman, 30, who boasts startlingly bright ginger hair, was the buoyant coordinator of the Kinder Swimpass, a protest swim so named for the mass trespass of Kinder Scout that took place 89 years earlier to the day. The original trespass was an iconic moment in the history of civil disobedience when around 500 ramblers marched over the plateau, the highest in the Peak District, in defiance of gamekeepers and the police. It caught the public imagination and marked a turning-point for the English land-access movement. National parks, footpaths and the right to roam are considered part of its legacy. Access to lakes, rivers and reservoirs are not. In England, Wales and Northern Ireland, inland waters – and who is entitled to enjoy them – remain contested territory. Hayman and the other swimmers that braved the cold hope to change this.

Hayman, a horticulturist, grew up on the coast where the sea always beckons, unrestricted, before moving to Sheffield for university. There, he turned to the reservoirs that dot the region, ignoring the signs designed to deter him. “I started to wonder: why isn’t this allowed?” he says. “Are these dangers what they say or is it actually just myths?” He discovered that most of Europe permits swimming in reservoirs and that in Scotland public rights of access to inland waters are enshrined by law. “That’s when I realised this is crazy,” he said. “There’s no reason we shouldn’t be swimming in these places.”

In 2016, he founded the Sheffield OUtdoor Plungers (Soup). It’s one of an impressive number of wild swimming groups with names that point to the eccentric British sensibility of swimming in a moderate climate and actually enjoying it. There’s FART – the Frensham Aquatic Recreation Team – Team Dash & Splash, the Isle of Sheppey Bluetits, Blue Balls Cold Water Swimming… I could go on. Soup was primarily a touchpoint to coordinate swims, but as with many of these groups, a hum of rebellion courses through the veins of its members. “As a group we are, obviously, advocating trespass,” says Claire Brown, 41, a Soup group administrator who took part in the swimpass, along with her 11-year-old daughter. For Brown, that day felt like a piece of history. “Hopefully we will look back on it as a pivotal moment.”

The battle over access to blue spaces has intensified. Wild swimming has surged with such ferocity over the past decade that even among its disciples it is now hard to discuss without an eye-roll (“We used to just call it swimming!”), and the banks are bustling. The pandemic, which left many with little to do but seek entertainment on their doorstep (cue jumping into freezing water), has only increased its allure. Soup membership has doubled in the past 12 months and now counts 10,000 on its Facebook group. Membership to the Outdoor Swimming Society grew by a third in 2020. Swim England counted 2.1 million people who prefer to swim in open water in 2019; a report by Outdoor Swimmer suggested that participation may have increased by between 1.5 and three times.

As pressure grows at popular spots it has led to a number of flashpoints as swimmers assert themselves against the laws, policies and landowners that so often obstruct the activity. When King’s College Cambridge banned wild swimming at the Grantchester Meadows in July, a petition opposing the decision drew 20,000 signatories and a protest swim was called. Swimmers who take to Bristol harbour have continued to flout a ban on the activity and are campaigning for a designated swimming area. When the City of London Corporation introduced compulsory charges at the Hampstead Heath bathing ponds this summer, locals marched on the heath with placards.

In Roger Deakin’s ode to wild swimming, Waterlog, the writer and environmentalist teases and provokes those who uphold a conservative, privatised vision of the land. Were Deakin still alive today, one imagines he would be pleased to hear of the agitation now stirring on English waters. In one altercation recollected in his book, he replies “sweetly” to an irate groundskeeper who accosts him post-swim. “Surely we should all have access to swim in our rivers just as we should be free to walk in our own countryside,” he says. “Don’t they belong to all of us?”

In August I drove up to Derbyshire to meet members of Soup. At Broomfield Reservoir I found Claire Brown waiting for me beside a sign: “Cold Water Kills – Bathing Prohibited.” We’re here to swim. The sign says the water is 12C all year round. “I’m not saying they’re lying,” says Brown, who has dark brown hair in a ponytail, glasses and a nose piercing. “But I’m not sure where they are taking that measurement from.”

Wild swimming has always had a subversive streak and since the pandemic the games of cat and mouse have heightened for Soup members. Brown tells me that last spring, after three group swims were intercepted in quick succession, she realised there was actually a mole from Yorkshire Water in the Soup Facebook group. The swimmers were forced to stage a polite eviction of their own.

Broomfield is Brown’s “gateway reservoir”. It was the first to draw her in the midst of a heatwave five years ago and she fosters a strong sense of ownership. As we enter the water, which has a dark reddish tint “like a brew”, she gives a running commentary on its features: a section of the bank that drops off more steeply; a cooler patch from an in-running stream; where there are rocks; to stay away from the dam – certainly not to jump off it… Swimming is made safer by a knowledge of the water and campaigners balk at “scaremongering” that, they argue, would be better served by clear information. When you take a dip and realise it is far warmer than 12C – and are not immediately sucked down a giant plug hole – one does question the integrity of the other warnings, even those that should be heeded. “If they are transparent about the risks,” said Brown, “people will trust it and make informed choices.”

Safety has long been used to justify swimming bans, particularly in reservoirs, though they are arguably less dangerous than the sea, lakes or rivers. The members of Soup are eager to cooperate with the water companies and local authorities to develop constructive ways to educate people, but they say they face an entrenched perception of swimming as a liability (despite case law demonstrating otherwise). In June, Mark Seymour, United Utilities catchment manager for Manchester, took a direct shot at experienced swimmers like Brown: “These open-water swimmers could indirectly be the cause of another drowning tragedy,” he said, before doubling down: “Reservoirs are completely unsuitable for swimming of any kind.”

But campaigners point out that the “just say no” approach is wearing thin; history has never favoured prohibition. Following a number of drownings in Yorkshire there have been calls for a different tack. Fiona Weir, an outdoor swimmer who previously lobbied to have “No Swimming” signs removed from Sparth reservoir, which now has open access, launched a petition in response to the tragedies. It called on local authorities and services to “use our experience to develop policies and practices that are based on evidence not fear and misinformation”.

The need to improve education about water safety can distract from a deeper issue; it should not determine the public’s fundamental right to swim in the water. These rights, wrote Deakin, “should no more be bought and sold than the right to walk up mountains or to swim in the sea from our beaches”. Reservoirs were privatised under the Thatcher government and the water companies have a legal obligation to provide access for recreational activities, but swimming is usually forsaken in favour of sailing, fishing and footpaths. Clubs with lifeguards operate at some, but a membership-only open-water swimming club is a very different operation to a free, communal beach. The Outdoor Swimming Society has worked for years to encourage landowners to shake off the default “no swimming” position and establish inland bathing spots of the sort that are so prevalent in mainland Europe. The writer Robert Macfarlane, a patron of the OSS, has said we should think of these places as a “new kind of commons”.

Rivers are similarly restricted, in this case by “riparian rights”, a system introduced under Henry VIII that grants the landowner ownership of the bank and the riverbed (no one owns the water). Of 42,700 miles of rivers in England, only 1,400 miles have uncontested access. While many larger rivers in England and Wales have a statutory right of navigation, access to and use of thousands of miles of waterways is determined by private interests. The validity of this is disputed; many argue that the Magna Carta gave people rights to the waterways and that a common law Public Right of Navigation still exists.

It’s an argument made by the canoe and kayak community. Paddlers have battled this system for decades and faced strong resistance from the angling clubs that are often leased the riparian rights by the landowner. The British Canoe Union has an ongoing campaign, River Access for All, and more recently, British Canoeing’s Clear Access Clear Waters campaign launched a petition that calls for clarity over the right to access rivers and lakes “free from challenge or threat”. Author and illustrator Nick Hayes examines the gradual lassoing of public land and water in the Book of Trespass: Crossing the Lines that Divide Us, published last summer. “Kayakers and swimmers slide through boundaries… and are too slippery for property rights to get a grip on,” he writes. “So they are categorically banned from all rivers and lakes that lack a specific act of parliament to give them access.”

The more that people do gain access to these spaces, the more unjust and abstract the regulatory framework that restricts them can seem. As Brown and Hayman discovered after their first forays into prohibited waters, once that invisible threshold has been crossed the spell is broken. Yet it takes a certain sort of privilege to feel comfortable with this ambiguity. Wild swimming is an overwhelmingly white pastime. The countryside can already feel unwelcome, or outright hostile, to ethnic minorities and the legal fuzziness around access can add to its exclusivity. As one friend told me, “The margins of error are smaller for non-white people, tolerance for rule-breaking is lower, there’s less benefit of the doubt and consequences are more real.” She added: “I always think twice about these small acts of freedom or dissidence. It doesn’t come naturally to feel like I have the right to do them.”

To liberate blue spaces of such invisible boundaries would only be one step towards making experiences like wild swimming more inclusive. Faraz Shibli, a travel writer, examined the legacy of the Kinder Trespass and the right to roam in The Great Outdoors magazine. “Access cannot just be thought about in legal terms,” he writes. “It has a social dimension too, incorporating culture, perception and prejudice.” The Right to Roam campaign recognises “that the walls of private estates are not the only barriers to people enjoying the countryside” and seeks to address the ways that “equal access to land is interwoven with racial equality, class equality, and gender equality”. As it states: “When the land is opened up to all, it is for everyone.”

At the village of Froggatt I meet Suzie Wheway, 40, a Soup member and open- water swimming instructor. Swimming is her life. It helped her, a mother of two, through a period of postnatal depression and remains vital to her mental health; being in water is not like standing in a field, or lying in long grass, she explains, it’s “being held”. Wheway and every wild swimmer I speak to are passionate about the urgentneed to remove barriers that restrict us from enjoying the natural world. “We need people to reconnect with it to be willing to then make change,” she says, adding that learning to be sensitive to the environment around swimming spots is part of the process of learning to enjoy it safely. As the Clear Access Clear Waters campaign puts it: “People protect what they love, but they only love what they know.”

We walk down to the River Derwent, past more signs from an angling club that implore us not to canoe or swim. It’s an odd experience being an outdoor swimming coach, Wheway explains: “We’re training these people, but where are they going to actually do it?” We reach the bank beside a stone arch bridge. After my temperate dip at Broomfield, Wheway is eager to give me a taste of some really cold water; this time it is 14C. We get changed and wade in – I’m gasping from the cold, but once Wheway reminds me I can breathe (if I choose to) – the feeling mellows and we make our way gently downstream. Or upstream. The water is so still it’s impossible to tell. When my skin starts to take on a burning sensation, we emerge at another bank where the evening sun beams down on a sloped meadow. I’m pulsing from the cold, and energised. “It can feel like a bed of nails,” said Wheway, “which can be enjoyable.”

The next morning the sky is bright and the air warm. Following in the footsteps of the Kinder Trespass, I march up into the hills from Hayfield. Once on the plateau, I look down to see the reservoir glistening in the August sun -winking at me. I could almost leap in. Sights set, I begin my descent, but the rain starts to close in. Soon I am completely drenched, sloshing my way down a path-turned-stream. My boots are heavy with mud. My map has turned to pulp. By the time I reach the edge of the reservoir, there is no way I could get any wetter; in that sense the decision had been made for me. In a moment that was more Shawshank Redemption than Bathers at Asnieres, I skip over a wall, peel off my clothes and plunge into the murky water.

I float, alone, looking back up at the lush green slopes now swathed in dark and misty clouds. As raindrops patter down around me I think of something that Wheway had said to me: “It just seems such an odd thing to say, doesn’t it? ‘Don’t do this!'”