The Southern Ocean around Antarctica is one of the world’s most important bodies of water. It drives ocean currents that affect our global climate and provides feeding and breeding grounds for some of our most iconic ocean species.

Ice Sheet, East Antarctica

2020 |70°46′ S 8°07′ E
distance unknown: 10 mins 17 secs
Water temperature: 0°C

The ice tunnel opened up in front of me and disappeared under the Antarctic ice sheet. It was the most beautiful thing I’d seen in my life. Even though I was freezing I kept saying to myself, ‘Slow down Lewis, take this all in.’ Then I heard an almighty explosion above my head; ice was shifting. I put my head down and swam as hard as I could.

My original idea was to swim across one of the 65,000 icebergs scientists had discovered on top of the East Antarctic ice sheet. But when my team found a river tunnelling under the ice, I knew we’d found the perfect location to highlight the rapid changes happening in Antarctica.

Anarctica is a high consequence swimming environment. Not only was the water close to freezing, but these supra-glacial rivers eventually rush down moulins, which plummet hundreds of metres to the bedrock below. The ice is also constantly shifting.

I spent the night before the swim trying to rest, but 24 hours of sunlight makes it difficult to sleep. The strong wind was shaking the tent’s flaps as my mind ran through all the things that could go wrong. In every swim I’ve undertaken, I’ve always had a safety boat next to me. Swimming down this tunnel I would be alone.

But once I entered the river I was totally present. The colours transfixed me; the ice walls started out a luminous turquoise, then became royal blue, then indigo, then violet. Midway through the tunnel I had to take my goggles off to see where I was going, and to avoid the huge stalactites hanging like daggers from the frozen ceiling.

All the blues in the world were not as beautiful as the light I saw as I emerged out the end of that tunnel. I had swum for just over ten minutes. It wasn’t possible to tell exactly how far I’d swum, because my GPS watch didn’t work underneath the ice, but when my team helped me out I was frozen to my core.

Once I’d got into dry clothes we still had to hike back to base camp – it took almost two hours, but at least it warmed me up. Sadly,  Antarctica is warming too: one week after my swim a record high of 20°C air temperature was recorded on the Antarctic Peninsula.

South Georgia

2017 | 54°S 36° W
1km: 19 mins 01 secs
Water temperature: 2.7°C – 3.6°C

I was about to swim in one of the world’s most important biodiversity hotspots, just off Grytviken, South Georgia, in waters no human had ever swum in before. But I was still shaken from my last swim three months previously, when I almost lost my life in the Arctic; I didn’t want to go through the trauma of severe hypothermia again.

When swim day dawned with clear skies and still waters, I knew cold wasn’t going to be a problem. But the wildlife was a significant issue.

In all my years of swimming, I had never had so much safety around me: safety paddlers Dawid Mocke and Peter Grantham in kayaks beside and behind; expedition leader Karin Strand with the stopwatch and blankets in the safety boat alongside; and Dr Roger Melvill in a high-speed rescue boat ready to race me back to the ship in the event of an emergency.

My Arctic swim taught me that, even with 30 years experience, things can go very wrong.

Given the likelihood of predators in the area, I decided to warm up by kayaking the route first, taking note of strategic landmarks – like the group of elephant seals around the halfway mark.

The astonishing wildlife here includes Antarctic fur seals, southern elephant seals, myriad whale species and vast colonies of penguins. This is the most important wildlife haven under British jurisdiction – and yet at the time only 2% of the waters around South Georgia and the South Sandwich Islands were fully protected. I was swimming to remind people of just what it is that we need to protect.

I dived in from the slipway in front of the scientific station on King Edward Point and soon settled into my rhythm, with Dawid counting time alongside. I prayed that the elephant seals – which can weigh up to 4 tonnes – would stay where they were, safely basking on the beach. And they did.

As I neared the old whaling station, I swam over whale bones on the sea floor, a reminder that more than 175 000 whales were slaughtered here. Now the oceans face a triple whammy: industrial overfishing, plastic pollution and climate change. Which is why full protection for this crucial ecosystem is critically important.

Half Moon Island, Bellingshausen Sea

2016 | 62°S 59°W
1km: 17 mins 18 sec
Water temperature: 0°C

I looked out of my cabin window Half Moon Bay spread out before me, a calm crescent of turquoise blue water punctuated by floating icebergs. Kayaker Dawid Mocke looked tiny paddling between those huge white monoliths, as he did his early-morning recce of the swim route. The former world champion would be my second on the swim that would launch the Antarctica 2020 campaign. With my support team behind me, and after consecutive days of training in increasingly colder water, I felt confident about the swim. I never imagined I would come so close to drowning.

People think the more swims you do, the easier it gets. But the toll on your body is cumulative, and every swim is unpredictable. This would be my 12th serious polar swim, and the first time my tongue would freeze.

I had only done a fifth of the total distance when I realised I was in serious trouble. At the 200-metre mark I began to take in water. Each time I turned my head to take a breath, I gulped in water along with air; because my tongue was freezing, I couldn’t expel that water from my mouth. It was a vicious circle.

I was terrified, but turning back was not an option. After our success in declaring the Ross Sea MPA, media attention was high. There are many more seas to save, and I have to keep doing these high profile swims until they are protected. So I just had to grind this one out.

With Dawid shouting encouragement and counting out the distance, we eventually got to the end. Over the next three years I’ll be attempting more swims like this one in our Antarctica 2020 campaign, until we have a chain of Marine Protected Areas around the continent of Antarctica to protect this magnificent ecosystem, and all the creatures who live in it.

I know the risk I face each time I swim down here. But without proper protection, the risk of losing these natural wonders is even greater. And that’s a risk to all humanity.

Cape Horn, Chile

2016 |55°S 67°  W
1st swim 850m: 16 min 47 sec
2nd swim 1000m: 18 min 22 sec
Water temp: 7°C

There is no section of sea with a fiercer reputation than Cape Horn. Its waters are wild, its rocks are treacherous, its currents unpredictable. All of which makes the tip of South America one of the most challenging places to swim.

But when we arrived there for a practice swim for my upcoming swim in the Bellingshausen Sea, the waters were calm and the day was balmy.

We had a few simple objectives: complete a long-distance swim around Cape Horn, get some cold water training before reaching Antarctica, and capture some arresting images at this iconic location. It turned out that was a few objectives too many.

The swim went well. The water a relatively comfortable 7°C, and there was no sign of the infamous swell that earned the area the nickname ‘sailor’s graveyard’.

The going was still challenging; competing currents from the Atlantic, Pacific and Southern Oceans all come together here, churning up the water and making it hard for me to see where I was going. But our photographer had a clear view, and got great shots.

Once we were back on board the ship, however, I was told we had only done an 850m swim, not the requisite kilometre for a long-distance swim. The last thing I wanted was to get back into the water. But the chance to do a long-distance swim around Cape Horn is a rare privilege, and 850 metres simply weren’t good enough. So I did the swim again.

In retrospect, I’m glad I did it twice. In training terms, the year leading up to the Antarctica 2020 launch had been my worst ever. I’d had surgery on my spine, and spent the recovery months shuttling back and forth to Russia to secure protection for the Ross Sea. Now I’d returned to Antarctica to swim for a network of Marine Protected Areas. Would my body handle the pressure of back-to-back cold-water swims?

You never know you’re ready until the moment you dive into the water. After those two practice swims at Cape Horn, I felt ready.

Peter I Island, Bellingshausen Sea

2015 | 69° S 90° W
560 m: 11 mins 11 sec
Water temperature: 0°C
Air temperature: 2°C

Fewer than 1,000 people had ever set foot on Peter I Island, one of the most remote islands on the planet. It was the site of one of the most memorable swims of my life.

We’d left the Ross Sea and were now in the Bellingshausen Sea, named after the Russian admiral. My mission was to appeal to Russia to support the call for an MPA in the Ross Sea, so I wanted to pursue any opportunity to connect with Russia. I got much more than I’d bargained for.

It was a startlingly beautiful swim. The water was crystal clear and the ice formations were astonishing. I swam alongside an iceberg for a very long time. When the edge of the iceberg disappeared under the water, I continued to swim over it for many more minutes. In my head, I’d known that only 10% of an iceberg appears above the water, with 90% below. But it seemed like the first time I really felt that fact.

There is so much going on underneath the surface of our oceans – rare and astonishing and beautiful things. Things we forget about, because they are out of sight.

During that swim, I realised that while I had been concentrating on promoting an MPA in the Ross Sea, there are 13 seas around Antarctica. All of them under threat, all of them deserving protection.

We need a network of protected areas that includes the Weddell Sea and the Scotia Sea, the Bellingshausen and the Amundsen, the Ross, the Mawson and the Davis Seas.

Immediately following this swim I would fly to Moscow and to Washington D.C. You have to immerse yourself in these polar waters to carry their message, but you have to go to the centres of power to get results.

It was the end of an expedition, but the beginning of the campaign of my lifetime.

Bay of Whales, Ross Sea, Antarctica

2015 | 78° S 164° W
330 m: 5 mins 0 sec
Water temperature: minus 1.7°C
Air temperature: minus 37°C

This was the big one: the swim that would finally get the Ross Sea protected.

The Ross Sea Ice shelf, rising straight up out of the Bay of Whales, was the most formidable thing I’d ever seen. Katabatic winds rushed down its face to meet the world’s southernmost body of water, bringing the air temperature down to a bitter minus 37°C. Was I really going to take off all my clothes and dive into that water?

We had been at sea for 15 days, during which time I’d only managed to do 740m of cold-water acclimatizing. And I was about to undertake the most dangerous swim of my life.

I rely on an amount of healthy fear to raise my core body temperature; anticipatory thermogenesis enables me to swim in extreme conditions. Panic undoes all that. It would be the first time I crossed the line between fear and panic in the water.

The weather was abysmal and we only had one small window of opportunity to swim. But we weren’t sure we could even launch the support boat.

At minus 37°C, the the air was so much colder than the freezing sea. Each time I lifted my arm out of the water into that air it was a drop of more than 35°C! The pain in my arm was more excruciating than the burning agony I felt in the rest of my body.

With each stroke I watched myself freeze. After 100m the first digits of my fingers were completely white. After 200m, the white had spread up to the second knuckle, at 300m I couldn’t feel my hands. At 330m I knew it was time to get out of the water.

I had undertaken the most southern swim in the world.  I would like to have swum further but I know that if I had stayed in that water any longer I wouldn’t be alive today.

On that day, my message about the desperate need to protect the Ross Sea came to life.

Cape Adare, Ross Sea, Antarctica

2015 | 71° S 170° E
540m: 10 mins
Water temperature: minus 1.7°C
Air temperature: minus 4°C

Cape Adare is dramatic. It’s hard to imagine how people overwintered here in those pioneering Antarctica expeditions. Let alone how I could swim here, amongst its enormous icebergs, in what would be the first swim in our Ross Sea campaign.

Forty percent of the world’s Adélie penguins live in the Ross Sea, and the biggest colony is here at Cape Adare. I love penguins, but I don’t want to be anywhere near a penguin when I swim in Antarctica, because where there are penguins, there will be predators. We’d already had one training swim aborted en route to the Ross Sea due to wildlife; I didn’t fancy my chances against a leopard seal or a killer whale.

On my last trip to Antarctica in 2005, I learned to throw chunks of ice into the water to replicate the sound a penguin would make if it dived in. If no predators surfaced in the next minutes, we’d assume the coast was clear.

That expedition was in midsummer, this one was later in the season, and further south. The difference in conditions was significant. I knew it would be a challenge, but I’ve been doing polar swims since 2003. I thought I knew what to expect. I didn’t expect to lose control of my hands.

At minus 1.7°C, the water was the coldest it can get without freezing over. I knew even before I jumped out of the boat that I didn’t want this to be a long swim; my next swim in a few days time would be even tougher. I decided to swim for 500m or 10 minutes, whichever came first.

In the end I swam 540m in 10 minutes. When I tried to grab the rope at the side of the boat, I couldn’t feel it. When they finally hauled me in I realised I couldn’t feel one side of my face. It was as if a dentist had given me too much aesthetic.

This was by far the most painful polar swim I had ever done, and there was an even harder one ahead.

On the plus side, the hot shower that followed was the most memorable one I’ve ever had!

Deception Island, South Shetland Islands

2005 | 62° S 60° W
1,6 km: 30 mins 30 secs
Water temp: 2°C

This swim still haunts me. I didn’t expect the setting to be so surreal – like something out of a James Bond movie.

Deception Island is a horseshoe-shaped caldera with black volcanic beaches and snow-white peaks. There was once a whaling station here, and we were told that the water gets so hot during eruptions that it can melt the paint off ships.

When we got there it was still an icy 2°C, and during the one-mile swim across Whaler’s Bay my core body temperature dropped to a dangerously low 33°C (hypothermia is clinically defined as a temperature below 35°C). The water was shallow in places, and when I first dived in I just couldn’t believe what I was seeing: whale bones everywhere. Hundreds of them, jawbones, ribs, long white spines … at times I was even touching them.

There was no single turning point in my life when I realised protecting the world’s oceans was what I was meant to do, but that moment was a major awakening. I resolved to make sure that that kind of decimation of marine species would never happen again in my lifetime, or beyond.

Petermann Island, Antarctic Peninsula

2005 | 65° S 64° W
1 km: 18 mins
Water temp: 0°C

The aim was to document what happened to my body during the southernmost long-distance swim ever undertaken, so we expected extreme conditions.

At the start it was snowing heavily; on the way back from the iceberg that marked the halfway point, it was coming down in chunks. Professor Tim Noakes was on the boat under a blanket watching the monitor, while Jonathan Dugas wrote vital statistics on a whiteboard to keep me informed. Suddenly, the information stopped coming. I didn’t know it, but the pen had frozen. Minutes passed. I pulled my head up and yelled, ‘WTF is happening?’ Tim started bellowing: ‘100 metres to go … 50 to go …’ He’d turned from doctor and scientist into coach.

When we finished the kilometre, we realised we’d forgotten to strap on the watch that carries my statistics from the heart rate monitor. We would have to do it all over again two days later. (See Deception Island above.) I was gutted. But I realised that the buck stops with me. Blame doesn’t solve problems and always leaves scars. We still didn’t have a basic checklist back then. We do now.

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