‘I want to jump in right now,” says Liz Richardson. She peers into the water, fully clothed but looking perilously close to diving in. Only last week you had to break the ice to swim in this natural pool on the edge of the Peak District. We strip to our costumes while her retriever, Hegley, covers our clothes in slobber. It’s mid-February and the wind slaps our bare skin. This is ridiculous. Richardson grins: “It’s living!”

Richardson is part way through the devising process for Swim, a four-person theatre show about the restorative powers of wild swimming. Two years ago, her close friend Lisa started to swim to help her deal with grief, after the deaths of her niece and nephew in the space of six months. “Now she swims every morning. She just has to dip her head under and have a moment away from everything.” After learning about her friend’s experience, Richardson began noticing a “community in the water” of people swimming as a means to cope. It’s not a cure, but it can be an aid. She wanted to understand the comfort of the water, and began forming the idea for a play.

Before we swim, we hike uphill for an hour and a half. Richardson is barely flushed. Having grown up in the Lake District, clambering up hills and leaping into tarns is second nature to her. “We didn’t call it wild swimming then. That’s just what you did: birthday, picnic, bridge jumping.” The water served as an equaliser. “There’s no judgment when you’re kids, apart from who can do the best jump.” This remains part of the draw for her as an adult. “In the water, everything else disappears.”

Facebook Twitter Pinterest ‘It’s living’ … theatre-maker Liz Richardson. Photograph: Kate Wyver

After taking a degree in acting at East 15, Richardson started doing standup and appeared at the Hackney Empire alongside Jenny Eclair. But her performing career was waylaid by a diagnosis of ulcerative colitis, an inflammatory bowel disease. After a few years in and out of hospital, she created Gutted, a one-woman show in which she talked frankly about her illness on a stage with three toilets. “I wanted to allow people to laugh at the awfulness that can occur when living with an IBD. I was giving them permission, rather than the uncomfortable awkwardness of not knowing what to say when you tell them your colostomy bag fell off in the middle of the pub.”

Richardson readies herself. Crouches down. Pushes off. How is it? 'Knives, thousands of knives'

For Swim, Richardson has chosen to work collaboratively with Josie Dale-Jones of ThisEgg and Sam Ward of YESYESNONO. The show will blend a narrative loosely based on Lisa’s story, with an expedition the group took to Richardson’s old haunt Wastwater, for Dale-Jones and Ward’s first wild swim. The trio are joined by musician Carmel Smickersgill, who is ironically – “brilliantly” afraid of water, says Richardson. They’ve set up rules for themselves to follow: no water on stage, and no cheesy underscores. “If you’re seriously going through a terrible time in your life, there’s no dramatic music going on when you’re out in the water. I want the reality, the honesty, the starkness.”

At the top of the hill, it feels like we’re the only two people in the world. Even the ducks have waddled off. Richardson steps on to a rock a few inches below the graphite-dark water, stiffens and starts jitteringly singing Circle of Life from The Lion King. “Carmel said it’s because when you’re anxious or excited, childhood songs are in your head.” It turns into a scatty Bohemian Rhapsody as she takes another step, ankles now ringed with silver.

With the help of bereavement charity Cruse, Richardson invited people to share stories of how they had been comforted by the outdoors. Responses were wide-ranging, including tales of grief, IVF treatment, menopause, postnatal depression and mental health issues. “I think it’s the sensation of escapism, the feeling of being held like a child and feeling lighter than you do on land.”

Facebook Twitter Pinterest Escapism … wild swimming at Wastwater

The water is only a few feet deep so you have to plunge in all at once. Richardson readies herself. Crouches down. Pushes off. How is it? She can’t speak for a moment. Then: “Knives,” she wheezes, “thousands of knives.”

I slide in after her. It’s hideously, gloriously, gaspingly cold. My feet touch what feels like thousands of eels – it’s the peat, squirming beneath my kicks. Richardson swims to the other side of the bank and loops round. We’re both panting, howling. The water is cold silk, turning to shards of glass where it meets the air. Gradually, our breaths steady, and we glide under the gaze of the hills.

One of the pleasures of wild swimming is the inability to get it wrong. “You can fail at the London marathon, but not this.” Alongside a planned run of the show at the Edinburgh fringe this year, Richardson intends to organise a weekly swim off the city’s Portobello Beach to offer festivalgoers this sense of distraction and revival. “It won’t matter what your reviews or audience numbers have been. None of that matters in the water.”

Too cold to linger, we soon clamber out. The wind thwacks our skin as we change, our bodies a shake of shivers and laughter. “It’s a no-knickers feeling!” Richardson yells from under her tent of a towel, practically exuding exclamation marks. The immediate physical sensation of it is overwhelming; I feel like I’m on fire. “You just forget everything, don’t you? I don’t think about anything other than this.”

Out of the wind, we thaw with coffee and biscuits. Richardson wants to bring Lisa here to camp soon. For her, the best part of swimming is going with friends. She looks around at the miles and miles of green and blue below. She shrugs. “Who wouldn’t want to share it?”