Pictures of the week: Llyn Llydaw, by Vivienne Rickman Poole

The peak of Snowdon obscures the late-afternoon sun just behind Vivienne Rickman-Poole’s head, as she cleaves through the water of Llyn Llydaw, allegedly the coldest lake in Britain.→ Photograph: Vivienne Rickman-Poole

Thousands pass this glacial lake every year on the way to the summit, but few are brave enough for a dip.→ Photograph: Vivienne Rickman-Poole

The water is as clear as glass, with a turquoise hue, and deep. It’s one of 18 Welsh lakes Rickman-Poole swam in last year: in April and September she set herself the challenge of swimming every day for a month.→ Photograph: Vivienne Rickman-Poole

September was warmer; on some days in early April there was ice on the surface. This year’s resolution is to swim in every lake in Snowdonia: there are around 250, so realistically, she says, this could take years.→ Photograph: Vivienne Rickman-Poole

But it’s a goal she’s happy to draw out – outdoor swimming near her home in north Wales gives her a chance to be alone, be mindful, and take in her surroundings.→ Photograph: Vivienne Rickman-Poole

Even a 10-minute dip leaves her feeling euphoric. “It’s the endolphins, as my friend calls them,” she says.→ Photograph: Vivienne Rickman-Poole

Passionate in equal measure about photography and wild swimming, she took this picture herself. Attaching a piece of elastic from her left wrist to her small, waterproof GoPro camera, she stretched her arm out just below the surface and released the shutter.→ Photograph: Vivienne Rickman-Poole

She takes her camera along to every swim and loves adding this element of creativity to her dips, snapping underwater or resting it on a float and operating it remotely.→ Photograph: Vivienne Rickman-Poole

Llyn Llydaw isn’t her favourite lake; that honour goes to Llyn Arddu, set below a steep cliff frequented by rock climbers, where she swims with friends. 'It’s crystal clear, the colour of the Mediterranean,' she says. 'Nothing but you, the rocks and the water.' Photograph: Vivienne Rickman-Poole