Doctors can't explain how extreme kayaker Ryan Lucas survived being trapped underwater for more than three minutes at a remote waterfall in the Kaimanawa Forest Park.
Lucas can - his expedition partner, Mike Roy.
The pair hit the headlines when Lucas was airlifted from dense bush near Turangi in the early hours of February 20 after a delicate rescue operation. His remarkable story of survival began hours earlier when Roy, a top Canadian kayaker, dragged Lucas' upturned kayak, which contained his lifeless body, from the rapids at the Tauranga-Taupo Falls.
Opening up about the February 20 accident for the first time, Lucas told the Herald he owes his life to Roy's quick actions and resourcefulness.
"I wouldn't be here if it wasn't for Mike, there's no question about that," said Lucas.
"What he did was amazing. Under the circumstances of what happened that day, I should be dead."
The Herald had been tracking Lucas' adventures for several months before his accident. He has a much bigger story to tell of the physical and emotional toll his sport has had on him. In 2015 Lucas' girlfriend Louise Jull, one of New Zealand's top female paddlers, drowned in the lower gorges of the Kaituna River. Lucas' drive to carry on in the sport after the tragedy is detailed in a full-length video and text feature The River People.
His latest ordeal began when Lucas, one of New Zealand's top white-water kayakers, was knocked out on impact after descending the 25m waterfall. The 25-year-old got his line slightly wrong as he went over the falls, and rather than entering the water nose first, he landed flat on the base of his kayak.
With Lucas hunched over to brace himself for the impact, his head slammed against the front of his kayak in the crash landing, causing him to black out. The force of the water at the foot of the falls then flipped Lucas' kayak.
Roy, who was on safety duties on the river below, knew something had gone seriously wrong when Lucas did not appear to be making any effort to right his upturned kayak.
"I was basically like a buoy just bobbing on top of the water," Lucas explained.
To get to where Lucas was, Roy had to paddle upstream against a heavy flow of fast-moving water, fighting the current with every stroke. By the time Roy reached his mate, he had already been submerged for nearly two minutes.
Roy frantically tried to flip Lucas in his kayak, but with the force of the water pinning him against a rock wall, the only way to free him was to attach a line to the kayak and drag Lucas out to the river bed. After finally freeing Lucas from his craft, Roy performed CPR on his Kiwi mate and revived him.
The pair's GoPro footage later revealed that from the point of impact to when Lucas was pulled from the water, more than three minutes had passed.
"I remember waking up and wondering 'what the hell happened?'" said Lucas.
"When I found out how long I was under the water for, I was pretty shocked. I can't believe I'm still here. That's just too long under the water."
But Lucas was nowhere near out of the woods, figuratively or literally. The pair were stuck in an isolated canyon shrouded by dense bush - it was a two-hour hike to get help and Roy was reluctant to leave Lucas. Eventually they decided to get back in their kayaks and continue downstream in the hope of getting cellphone coverage.
They paddled for about an hour, but with darkness beginning to set in and Lucas' condition worsening, they had to stop.
"I remember Mike telling me we'd have to walk out, but I just couldn't walk. I couldn't breathe," said Lucas.
With Lucas at risk of lung complications and hypothermia, Roy knew he had no option but to leave his buddy alone in the bush and go and get help. He wrapped Lucas in a survival blanket and built a fire, while Lucas worked on trying to stabilise his breathing.
"I told him to leave. He didn't really want to leave, but I just kept telling him to go," said Lucas.
"It did cross my mind that I wouldn't make it out of there, but I kind of got to the point where I accepted that ... I had gotten myself into that situation; it was my error that led me there."
Roy had to climb 100m up a canyon wall and walk 5km along a forestry track before he was able to get cellphone coverage to call for help. It was after midnight when the emergency call was finally made, triggering a search and rescue operation involving police, St John Ambulance, LandSAR Turangi volunteers and the Greenlea Rescue Helicopter.
Using the mobile phone, the helicopter and ground crew were able to log Roy's general position in the wilderness and, using night vision googles, spotted the injured man stuck in a narrow, steep-sided part of the river.
Greenlea Rescue helicopter pilot Nat Every described the rescue as a "bit of a developing story", with the rescuers only discovering the full extent of Lucas' ordeal once they reached him on the ground. After helping guide the ground crew through the steep terrain to Lucas, Every was preparing to leave the troops to it before he got the call he may be needed to stick around.
"We got a call to say he's a bit uncomfortable and was making really slow progress [on the hike out], but at that stage it didn't really meet the threshold for needing to lift him out.
Then a couple of minutes later they came back to us and said 'he's coughing up blood, we're a bit concerned he may have a punctured lung from CPR' at which point we had to give it the old 'I'm sorry, can you say that again'?
"At that stage we thought we better investigate hoisting this guy out."
Given the inherent risks involved in winching a patient out, Every said he will only perform the manoeuvre in life or death situations. On its own, hoisting is fraught with issues - hoisting at night unfurls a whole new set of challenges.
"I was operating on night vision goggles, which affects your depth perception, and operating in a river valley where there's not a lot of room in there and you're hovering there with a 100-odd foot of cable hanging out the side of the helicopter," said Every.
Lucas is well aware of the risks that were taken to get him out safely.
"I'm so thankful to the helicopter pilot and the crew for what they did for me."
He was flown to Taupo Hospital suffering from lung complications, hypothermia, concussion and damaged ribs. Remarkably, he has not suffered any long-term health problems from the incident.
Jonathon Webber, chief executive of Watersafe Auckland, said overseas research has shown that in drowning cases where patients have had good outcomes, 88 per cent were submerged for less than six minutes, but the critical factor was CPR being administered immediately.
"It's really the immediate interventions of those people on the scene that make the difference," he said.
"Whilst the sort of things the paramedics do in terms of advanced airways and drugs and those sorts of things have a place, they're not actually the primary thing that saves a person's life, it's just plain old-fashioned basic CPR without equipment that does it."
Given the prolonged period of time it took for Lucas to receive proper medical treatment after he was revived, Webber said Lucas was "very, very lucky".
Despite the "very scary and crazy" experience, Lucas, who has paddled some of the most remote and treacherous stretches of river around the world, said he plans to keep kayaking.
"I still love paddling. I'm going to try and put that incident to the side and keep going. Be cautious, but keep going."
"It just shows how important it is to surround yourself with good people who know what they're doing on the river."