As she hammered desperately to free a split pin holding rigging of the 15m fibreglass boat, one false move meant she would plunge into the freezing waters of the Southern Ocean, 1000 nautical miles from the nearest land and be lost forever.

“I went through that horrible moment that instead of maybe dying in the next 24 hours, I was potentially dying in the next five minutes,” she recalls, of her perilous fight for life during her record-breaking circumnavigation of Antarctica last year.

Sitting aboard her yacht, Climate Action Now, in the calmest of waters at Sydney’s Darling Harbour, a breeze barely troubling the water, Blair is quick to smile. She exudes energy, talking with verve about the night she almost died and how inspired she is to try and raise awareness over climate change.

In spring, she is planning to become the first woman to circumnavigate Australia solo, non-stop and unassisted, a voyage that will see her sleep for as little as four hours a day and for 10 minutes at a time.

At 33, she might look like the girl next door, with her chestnut hair shining in the winter sun, her piercing blue eyes and a ready giggle, but she is crafted from sterner stuff. That she is here at all is testament to her incredible mental and physical strength.

Caught in the mother of all storms, someone without true grit may have given up and submitted themselves to the ocean. But not Blair.

She battled, terrified, for four soul-wrenching hours to save her ship — and herself — while monster waves the size of a two-storey building pounded her yacht, the mast rent in two, hanging over the side and caught by its own ropes and stays, sawing a hole in the deck.

She was down below, her boat being tossed in the tempest, when she heard her rigging lines snap.

“As I was clipping my life jacket shut, I then heard the mast snap, a deafening, horrible sound of aluminium ripping and grinding. The whole boat shuddered. You don’t know how bad it is because you are inside the boat and you can’t see. I froze, for about five seconds, but it felt like forever.

“I remember thinking I could die. Once your mast is gone, you could roll the boat, you could have the mast puncture the boat and sink it. Even if I got into a life raft, I could die from exposure, so my chances of survival went from ‘four weeks and I am home’ to ‘hang on, in the next 12 hours I could be dead’.

“That reality crashed down on me in that second. I thought: ‘I have to cut the mast free, because that’s the only way to save my life and save the boat’.

“If I lost the boat I knew I was a goner. It was a matter of fight and save the boat at any cost because that would give me half a shot.”

She gave it her better-than-best shot, scrambling about the deck, trying to avoid being speared by loose rigging or having a limb broken by the pounding, broken mast, freezing and soaked, clinging on, clipping on to the safety lines, desperate to release the lines holding the broken mast.

Grabbing tools she crawled to the back of the boat to see the mast tearing a hole in the hull deck join.

“All my rails were gone on the starboard side so there was no safety from getting washed overboard there and, because I was now stationary and effectively at anchor in storm water, waves started to break completely over the top of the boat, so every 30 seconds I would be submerged up to my hips and if I was working low trying to do something, I would be going completely underwater.”

It took her half an hour to free the split pin on the back stay, stopping only to issue a “pan pan” — a distress call one step before calling a mayday — although the nearest help was three days away.

“I was in shock and just reacting. I had that constant feeling of almost bursting into tears,” she says.

Crawling to the front of the boat in pitching and rolling seas, Blair had little to hold on to, and had to unclip her safety line to get past the deck’s debris.

“I was in shock and shivering uncontrollably, I had put foul weather gear on but I was soaked through to the bone.

“I needed to ditch the mast in such a way that it didn’t rip off the deck of the boat, because if it did then it would take seconds to sink the boat.”

Blair realised her only option was to sit on the bowsprit, which overhangs the water outside the boat, to release a pin holding the forestay.

“That meant I would be completely exposed. I would be clipped on but it was almost a certainty that I would get washed off.” By that time she had been battling for about two-and-a-half hours and was going numb.

“If I had have gone in the water my chances of climbing back up were slim to nil. I was losing the feeling in my hands and the dexterity in my fingers.

“That was the most terrifying part of the whole experience because I had to make the decision between not doing it and sink the boat and a certainty of death or taking the risk to try to hold on and make it happen and maybe make it back on board.”

She climbed out, managing to cling on, hammering the pin in between each wave.

“In the moonlight, I could see and hear the white water coming. Every time I heard it, I would grip the rail and hug the boat as hard as I could while the wave smashed into me and broke over the top.

“I would have to let go completely, with the screwdriver in one hand and the hammer in the other, and I would have to hit, may be three times between each wave, and then hug down and hold on again. It was a do-or-die moment.”

Finally, with the mast released, it broke free and sank. Now hypothermic, she went below and hugged water bottles for hours to warm up, eventually being refuelled by a diverted container ship, before motoring to Cape Town. After two months of repairs, she set sail for home and completed the record.

For someone who has stared death in the face and won, it’s hard to believe that Blair would throw herself back on the mercy of the seas to take on another challenge so soon — especially one as perilous as circumnavigating Australia.

She will not only have treacherous reefs and capes to contend with, but will also have to keep an almost permanent watch for other ships and hazards from ever-increasing flotsam and jetsam.

Blair’s aim, apart from the record, is to raise awareness about climate change, urging people to do small things to help the environment.

“When I started sailing I would see debris in the water. Now I notice lots of rubbish and also the weather pattern shift over the years. Weather used to be predictable. It is not any more.

“I want to raise awareness of the issue of climate change,” she says.

In keeping with her sustainability message, Blair’s boat will be 100 per cent eco-powered, with new wind, hydro and hydrogen generators and solar power support.

“People think this circumnavigation is easier because Australia is right there, about 30-50km away for most of the trip.

“But there is all the commercial shipping all around Australia, which means I have to keep a good lookout and won’t be able to sleep very much. In shallow water, instead of the rolling ocean swell you get the peaky, steep, sharp little waves and I have nowhere to run.”

She hopes to set sail in September amid fine weather.

With her wide grin, Blair adds: “The one thing about solo sailing, though, is that I win every argument.”