The Arctic Ocean is a crucial barometer of climate change. It’s a place of extremes, and I’ve witnessed extraordinary changes over the decades I’ve been swimming here.

Edge of Arctic Sea Ice

2017 | 78° N 16° E
1km: 21 mins 29 secs
Water temperature: minus 0.1°C – minus 0.6°C

This one took me to the very edge. I don’t just mean the edge of the sea ice: I almost didn’t come back from this swim.

I’d scheduled cold-water training, but when we reached the High Arctic the water at Longyearbyen was 10°C. When I last swan there in 2005 it was a brisk 3°C. The very reason for my swim was to draw attention to the fact that the Arctic is changing, but the speed of runaway climate change, 7 degrees in just 12 years, took us all by surprise.

When we eventually reached the edge of the Arctic sea ice at 80°N, conditions were perfect and the water temperature hovered just above minus 0.6°C. I was in my best pre-swim condition ever, but hadn’t done any preparation time in cold-water.

I knew there was a problem the moment I dived in. The high-latitude sun angle meant I couldn’t see my safety paddler’s signals; I started counting strokes to measure my distance, but my cadence was off and I miscalculated.

Exactly ten years ago to the day, I had swum across the North Pole. I got through that one by breaking it into manageable chunks. So this time, when my frozen hands couldn’t grip the water at 650 metres, I told myself to squeeze out another 50 metres. I pressed on to 750m, then 800m. At 900m my body started shutting down; somehow I crawled through the last 100 metres.

With close to 22 minutes in the water, this was my longest ever sub-zero swim. It took its toll; afterwards I was bruised all over and it took a very long time to warm up. Each swim gets harder as I get older. I knew I would need a very good reason to get back into freezing water again.

Watch SKY UK’s “Arctic Peril”

North Pole

2007 | 90° N
1km: 18 mins 50 secs
Water temperature: minus 1.7°C

I had never been more frightened than I was standing on the edge of the sea ice.

Minus 1.7°C was the coldest water any human had ever swum in. The previous day’s test swim had gone horribly wrong. The water was ink black, and it was 4.2 long, cold kilometres to the bottom. And there might be polar bears.

But the reason I was right to be terrified, was that I shouldn’t have been able to swim at the North Pole in the first place.

Two years previously, 23% of the Arctic ice cover had melted. I was swimming to draw the world’s attention to the effect of climate change on the Arctic.

The swim took 18 minutes and 50 seconds. And the combined efforts of a dedicated team that kept hold of the vision. Their motivation turned an impossible kilometre into 10 hundred-metre stretches that each seemed possible.

Each section represented a nation, and the people who brought me here. Their flags spurred me on.

Watch the TED Talk

Verlegenhuken, Spitsbergen, Norway

2005 | 78° N 13° E
1km: 20 mins 30 secs
Water temperature: 3°C

The Inuit have a saying, “You know who your friends are when the ice breaks beneath you.” I don’t have to walk over thin ice to know who my friends are; they all came with me to Verlegenhuken.

It was also the only time I ever had a disagreement with Prof Tim Noakes.

I had just swum across Magdalene Fjord, at 79° North. That was a perfect swim, but 80° sounded even more tantalising. I wanted to do the world’s most northern long-distance swim there.

Verlegenhuken means Point of Desolation’, and it lived up to its name. Temperature alone doesn’t tell the full story; the weather conditions can make the difference between a challenging swim and a miserable one. The weather that day was miserable, dark and cold. The sleet lashing the black rocks made the prospect of 3°C water even more forbidding.

Tim felt that a second swim in the space of 12 hours was just too much for my body. But I was determined. He also said he’d never ever seen a more inappropriate place to do a long distance swim. I had to agree with him there. So I promised I would get out of the water the minute he asked me to. Thankfully, I managed to complete the kilometre before he did.

Magdalenefjord, Spitsbergen, Norway

2005 | 79° N 10° E
1km: 21 mins 30 secs
Water temperature: 3°C

No matter how much preparation you do, you only know how good your team is when they’re up against it.

Our team for the most northern long-distance swim was made up of Brits, South Africans, Norwegians and a Dane, whose job it was to keep an eye out for hungry polar bears.

It was also my first swim with renowned Sports Scientist Professor Tim Noakes, and the first time I experienced his professionalism under pressure. We had taken our outfit to another level. (This same core team would go on to face much harsher conditions in Antarctica, the North Pole and Mt Everest.)

Here’s what I remember about this swim: a massive turquoise glacier feeding into the fjord, with ice chunks as big as buildings breaking off and landing in the 3°C water to form floating icebergs. I swam past them with my head in the water and what did I hear? Snap-crackle-pop – like Rice Krispies. It’s the sound of tiny air bubbles being released from the ice – air that was trapped there as much as 3,000 years ago. To swim through this sound is to swim through history.

North Cape, Norway

2003 | 71° N 25° E
5 km: 1 hr 4 mins
Water temperature: 8°C

It was the first time I visualised an entire swim from beginning to end. I first saw the North Cape’s spectacular cliffs, which rise straight out of the Arctic Ocean, from a small zodiac with Ben Smith, my wingman for the world’s most northern swim. I imprinted every crag and every valley so I would know how far I’d progressed, and how far I still had to go, during the swim.

It would be particularly challenging, not just because of 8°C water, but because I was so thin.

We were serving in the British SAS at the time, and could be deployed at any moment to the Middle East. Here’s the problem: I was training to do my coldest swim to date, but I had to be lean and fast because at any time I might be running around in the desert. No insulating body fat allowed.

But there was a warm fire waiting for me on the beach when I completed the first ever swim above the Arctic Circle. A herd of a reindeer had gathered there too. It was the beginning of my love affair with Norway.

Spin the Globe

Explore the world and see where Lewis has swum. Click on any pin to find out more about that particular swim.

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