He swam 7km through waters infested with saltwater crocs, box jellyfish and venomous stingers while coping with huge tides and avoiding container ships.
In doing so, Michael Wells became the first person to swim across Darwin Harbour, a feat so risky that he was accompanied on both sides by sea kayakers and boats, with an escort boat ahead and a professional croc-spotter on board.
It was worth it though - Michael raised A$18,000 for breast cancer research in honour of his sister Susan Wells, who died of breast cancer in 2017, leaving husband Colin and son Gabe.
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Now Michael, 56, is tackling a different but no less difficult challenge. In two weeks, he'll attempt to become the first person to breaststroke the 40km length of Lake Taupō, again to raise money for breast cancer research.
In 1955, Kiwi Margaret Sweeney became the first person to complete the epic swim. Only 60 or so swimmers have managed the feat since, and no one has completed the swim using only breaststroke.
Michael says modestly that he's not a swimming champion but ever since he was a child, he has had a knack for breaststroke and even swam in the Western Australia championships.
"I wouldn't have had a look in with other strokes".
"With breaststroke I can go forward whereas with freestyle I can hardly do a lap or two but breaststroke feels natural to me. It's like going for a walk."
Although he is Australian, the funds Michael raises in New Zealand will go to breast cancer research in New Zealand.
"Susan loved New Zealand, and not long before she died she had a family holiday here," Michael says. "She told me she enjoyed herself so much that there were times she forgot she had cancer. New Zealand gave a special gift to Susan and her family, and I would like to give something back by raising money for women in New Zealand affected by this terrible disease."
The swim is scheduled for the weekend of February 8 and 9. Open water swimming legend Philip Rush, who holds the record for crossing Lake Taupō in 10 hours 14 minutes, is Michael's coach, and will escort Michael across the lake during his swim. The swim is likely to take about 16 hours, starting at about 3am at the southernmost point of the lake.
Michael says he originally came up with the Darwin Harbour swim as a way of dealing with his grief over Susan's death. She was just 50.
"I went to a counsellor and she said 'everybody finds it difficult to cope and feels they have to do something'. I wanted to come up with something that could be useful and I came up with the idea that I'd swim breaststroke across Darwin Harbour and when I was doing it, I realised I was the first person to cross Darwin Harbour using any stroke."
He was happy with the money he raised and thought he was done, until a colleague visited Taupō.
"She saw a sign about the Lake Taupō swim and how nobody did it until 1955 and she sent me a picture of it saying "hey Michael, this could be your next challenge"."
While Michael knew he couldn't break the speed record for the Lake Taupō swim, he did think he might be the first person to do it breaststroke.
He contacted Philip and has been working with him to prepare ever since. He says Philip is "cautiously optimistic" that Michael has done the training required, although luck will also be needed for good weather and calm waters on the day.
Initially Michael planned to swim without a wetsuit but realised after arriving in Taupō last week and taking a dip in the lake's 20-degree waters, that that was going to be impossible. He's purchased a swimming wetsuit, an entirely new experience for a man from tropical north Australia.
"I worked out quite quickly after I got here that it was a certainty that if I spent 16 hours in the water I'd get hypothermia. I had a few swims just in my speedos and it was very, very cold and my body wasn't able to deal with it for more than short periods, and Philip agrees."
Michael hopes, if all goes well, to be finished by 7pm on the day of the swim. He'll be accompanied by Philip in a small boat, and there will also be a larger escort boat alongside. He's heartened that his two adult children, his former wife and sister Robyn will all be aboard to support him.
"Whatever Philip asks me to do, I'll do. I'm just so determined to give myself the best chance. The last thing I want to do is be pulled out of the water three-quarters of the way through because I haven't put the work in.
"I had these moments of dread with the Darwin swim where I thought 'why have I committed myself to this, no one's making me do it', but I got through that and I feel that that's one of the greatest achievements of my life."
* To support Michael visit givealittle.co.nz/fundraiser/swim-for-susan-aotearoa or search 'Michael Wells'. The money raised will support the New Zealand Breast Cancer Foundation's work in improving early detection, investing in life-saving research and providing patient advice and support.