I’m perched on the muddy bank of a river, working up the courage to enter the water. Hovering on the surface are what looks like an extended family of spidery bugs – water boatmen, apparently. “The presence of wildlife is a good sign,” says my swim guide Ella Foote, AKA the Dip Advisor, ignoring my grimace. “They need oxygen to breathe, so they indicate good water quality.”

I slither in and the icy cold water is a shocking contrast to the sizzling hot weather. I start to freak out a bit. “Try to calm your breathing,” says Ella, who know it’s my first ever wild swim. “We have all the time in the world.” I try to recall the yoga classes I once took, shut my eyes, and give it my best shot. It seems to do the trick, and I begin to acclimatise to the water.

Swimming outside in natural bodies of water – from lakes and rivers to the sea – has seen a massive growth in popularity over recent years according to a Sport England Active Lives survey. And with only 20% of UK swimming pools thought to have reopened since lockdown, plus the continued good weather, numbers are increasing.

But for those of us who don’t feel confident enough to give it a go – I panic when I’m out of my depth and can’t tread water – friends’ Instagram pictures of blissful dips in the wild have just inspired envy.

Which is why I’ve signed up for a session with Ella, an open water lifeguard and swimming teacher who offers one-to-one “bespoke” swims, mainly in the home counties, and scheduled 1km and 3km “journey swims” on the River Wey in Surrey for groups of up to six.

We meet at Woking station, from where it’s a 10-minute drive and short walk across a meadow to our swim spot on a secluded branch off the navigational channel of the River Wey. “Little Wiggle,” as Ella calls it, is too shallow and winding for boats and hidden from passersby.

Just as well, as a bright orange tow float bag and an inflatable woggle are now clipped round my waist, and I look more sausage than swimmer. It’s reassuring though. I’m not a complete swimming novice (you need to be able to swim 25 metres for Ella’s session), but always need to know my feet can touch solid ground.

My Indian parents were not strong swimmers – they grew up in a troubled South Africa, and had more important things on their mind. As a child, living in Canada, I’d stick to the doggy paddle at outdoor pools, and at university I learned front crawl. Eventually I joined a gym with a pool which had no deep end and taught myself the breaststroke. I love open water, have been sea kayaking, snorkelling (with life jacket) and I’ve taken dinghy sailing lessons, but because I can’t tread water, the underlying anxiety is always there.

Ella instills complete confidence, though, with patience and reassuring presence. “I work hard to understand each swimmer’s needs. If you can swim confidently and consistently in a pool, I can help you. The more honest about your ability, concerns or fears, the better I can design the experience.”

“For me the emphasis is on enjoyment, and taking the time to notice the nature around us. I love nothing more than to see people’s eyes light up with delight. And I want swimming to be inclusive, the water is for everyone,” she continues. As a plus-size woman, she has not always felt welcome in outdoor spaces, she says.

Ella advises that beginners never swim alone, research where to get in and out (there are plenty of websites and books offering advice), get in slowly, always swim sober and use common sense. It’s crucial too to be mindful of the local area and wildlife, leave no litter, and avoid busy spots.

Once I warm up, we plunge forward. At first I’m tentative, clinging to my noodle for dear life, but with Ella’s guidance, I begin to relax, and glide along with the current as I float downstream. The banks are a tangle of reeds and wildflowers: we pass yellow water-lilies, we’re bathed in sunlight, and overhanging trees sway in the breeze. I feel a rare peace descend. “Kingfisher!” says Ella, and I turn to see a flash of blue. Dragonflies and delicate damselflies cross our path, and butterflies dart along the bank.

We’re entirely on our own for the duration, and being in the water at riverbank level is a nature connection at its most immersive. Water reeds brush against my legs, and I can feel woody “bits” underfoot, but their solidity is reassuring. At a bend in the river, the water deepens, and though I’m still using the aid, my grip has loosened – in fact, I’m more buoyant in the deep water, my enjoyment amplified. For the last 50 metres or so, I’m so chilled, I do the breaststroke. Ella compliments my technique and I glow. When we reach the bank, I feel euphoric, reborn. Never has swimming felt so good. There and then I make a promise to myself that I will learn to tread water. I want to return to this stretch of the river, and swim it all the way along.

Guided swims on the River Wey (the ‘Wey Wiggle’) with the Dip Advisor last around 90 minutes and include refreshments, from £45pp for a 1km swim to £55 for a 3km swim