Australian adventurer Dan Bull set the record for swimming in the world’s highest lake, but the time in the water was brutal and could have killed him. He completed the feat in January and Guinness World Records ratified it in August.

Bull swam 100 metres at 6,400 metres in an unnamed lake on Ojos del Salado, the world’s highest volcano, in Chile. He had attempted the same feat in 2018, but the lake was frozen so he completed the world’s highest kayak instead. Bull arrived earlier in the year for his second attempt, but it was still terribly cold.

“During the swim it was excruciating, it felt like 1,000 knives stabbing at my body with each stroke. I had to keep reminding myself of the goal and make a decision to keep going,” the 39-year-old said.

It was so cold a cardiologist warned him not to go as the shock might kill him. Bull trained in cold showers and ice baths to prepare.

Dan Bull celebrates setting the record.

“I always take on medical advice,” Bull said. “But this was the only time I knew I had to ignore it to pursue this challenge. The risk is there, I have to take it seriously, but how can I prepare as best as possible to mitigate the risks.”

So much time and effort went into the attempt, but it almost came undone. The day before the swim, Bull’s team of mountaineers dropped out, unwilling to be party to the risk.

“They only told me the day before the event, so I had to go back down and find less experienced, but more motivated climbers to go back up again. In this case, being motivated over experienced won out,” Bull said.

Finally, after years of planning, Bull stood in his swimming trunks on the edge of the lake.

“It was incredible. Just before the swim, there was a moment when everything had finally come together. There were a number of setbacks along the way. All these obstacles had been overcome to try again.”

Even reaching the lake was an ordeal, made harder still as his team bailed out the day before.

“That was profound, even more so than when I had completed it, because I realised I was going to have to take the plunge despite the challenges up to that point. This was going to be the make or break, the potentially deadly stage.”

Once he completed the swim, Bull dived into his tent and surrounded himself with his team to warm up. He wore a full down suit, but was careful not to heat up too quickly as that can provoke heart issues.

“Once we got off the mountain, it started to sink in. Reflecting back, there was a huge amount of satisfaction,” Bull said.

“Compared to other expeditions or feats, which have a more measurable and immediate sense of sanctification, with this one the concept of achieving something that was not achievable enabled me to push through but took time to reflect on.”