Between the two hulls of our catamaran, the waves join together and almost double in size before hitting my sled. I am apprehensive about getting on it the usual five minutes in advance of zero count, which is when I must begin my descent, but the sight below me is even more stressful.
One of my deep safety divers, Dave, is due to take up his position at 130m but doesnt seem to be able to equalise below 6m and he is frantically massaging his ear, tipping his head and adjusting his depth as John and Mark disappear out of sight on their way to 110m.
As the seconds tick by I grow concerned that he will not be in place by the time I pass through 130m, where we have agreed that he will tap his metal sticks together.
I fix my eyes on my husband Paul. He is calm and his gaze is an instant comfort. On the boat, Simon calls out: Five minutes! As I open my mouth with worry, Paul is already considering a solution and issues an instruction for another minute to be added to the countdown. He knows that I should save my breath for the dive.
hspace=5 In a routine that we have done 13 times before, during training dives, I mount the sled, and within seconds Paul has placed my long fins inside the wedge and is clipping a safety line onto a harness around my waist. The line attaches to the harness at the back at one end and to the rope above the liftbag at the other, so that I am always connected to the dive rope, but never to the sled itself.
As is habitual, I fiddle with the brake system and set it so that within half a turn the sled will stop completely. Then I glance up to the release clip to make sure it is mounted to release with a gentle tug to the right. Finally, I reach higher and test the valve on the tank that will fill the liftbag for my return journey, but I am careful not to close it too tight, in case the added pressure at 160m makes it impossible for me to open.
All this is hard to do with the waves sometimes completely submerging me. At two minutes to go, I repeat my check-over of the sled before slowly reaching for my noseclip.
My female competitor in No Limits uses an equalisation technique that involves flooding her sinuses, for which I admire her, because it isnt a pleasant sensation, but the advantage is great - there is no need to equalise at all, so her dives are much faster and, in theory, there seems to be no limit to the depth she could achieve.
But Frenchman Loic Leferme set the mens world record in this discipline at 154m with the noseclip, and in training I hit 156m, so I am confident of my technique.
With 15 seconds to go, I begin my last breath, and when zero is called I am using a technique to pack extra air into my lungs when I am struck hard by a wave.
Caught between two forces - the thoracic pressure I am increasing through packing resulting in dizziness, and the wave pushing me forward hard - my face hits the sled, knocking the noseclip off. Paul is in front of me, asking if I am OK, and Simon indicates that we are 20 seconds after zero.
I turn to the judge to ask if he has a problem with me still going for it and he quickly responds that he doesnt. The rules dont specify that I must go within a particular timeframe, but we have trained this way to ensure that the divers spend as short a time at their appointed depths as possible.
I repeat my last breath again very quickly, barely packing at all, and within 20 seconds of the incident, I am gone.
The first thing I notice is that, beneath the surface, the water is utterly calm. I barely need to hold onto the sled, as I did on the surface. It does, however, occur to me that perhaps my final breath was insufficient in terms of volume for such a deep dive. Will I have enough air to equalise so deep
In training I was able to clear my ears for the last time at around 130m and my eardrums stood up to the increasing pressure of the last few metres, even as deep as 156m. Of course there is discomfort, but it is tolerable. But I had the advantage of a deeper breath on those dives, and this is the dive that matters.
Its not in my nature to give up without trying, so I let the sled fly deeper, open my eyes at 40m and signal OK when I sense that the divers are around me. Eighty metres comes fast, and Andre signals the depth with his clangers. Slowly I reach above me for the tank valve, and crack it open enough to allow air into the liftbag, allowing me to maintain my current speed.
It is at around 110m, approximately a minute into the dive, when it becomes abundantly clear that I do not have the usual volume of air in my lungs needed for deep equalising. I close the valve and quickly begin braking the sled to give me more time to find whatever air I have left and force it into my Eustachian tubes to relieve the pressure on my eardrums.
It works, but it is the last time. I proceed slowly down the remaining 50m of rope, taking a full minute to monitor carefully the increasing pressure in my ears.
The rate at which pressure increases at such depths is slow, and even slower as the depth increases, so taking time in this portion of the dive seems the only way.
Then there is Dave, tapping as requested and encouraging me verbally, which I can clearly hear thanks to his rebreather. At these depths free-divers experience a degree of narcosis, but I think that having to focus so intently on my ears actually helps me to overcome it.
The sled stops with a jolt at a big knot in the line at 160m and I open my eyes. On only two other dives, when I hit 152m and 154m, have I seen this darkness, and it surprises me again.
I take a moment to look around, out of the glare of the lights placed on two cameras pointing at me, then I raise my hand to my mouth and blow a kiss to the deep.
As the seconds tick by, I place my left hand on one of the handlebars to the liftbag, and my right on the tank valve, opening it wide.
Something makes me stay for a while, just a few more seconds, and then I pull the quick release and begin the return journey.
The speed surprises me, because I dont normally fill the liftbag so much, and then I realise that I am still dumping air into it. Thoughts are incoherent with narcosis, and senses are delayed, but the noise of air racing out of the valve makes me focus and I reach up to turn it off.
As I race back past Dave he is yelling encouragement. Seconds later I hear John singing Brown-Eyed Girl and catch a glimpse of him and Mark before the speed of my ascent prevents me from opening my eyes again.
At 80m, Andre taps again to let me know that I am halfway there, and soon after I am enveloped by a torrent of bubbles escaping the liftbag as the air increases in size. The final taps come at 40m, barely audible among the incredible turbulence and 20m trail of bubbles that surround me. That is my signal to release my safety harness, so I reach behind me with my right hand to find it.
I like to swim the last 20-25m because I think those last two changes in pressure are tough on the body at such speed. When I pull the clip, nothing happens. Again - but I am still not free.
For some reason there is no tension on the rope, so the clip has no traction to pull against. I let the bag slip from my grip a little and eventually, about 5m from the surface, I am free.
In the bubbles I search for Paul but he is nowhere. He had been waiting for me at 20m as I zipped by, so I surface without him. I want to tell him first that I did it, beneath the waves in silence where I will be able to see him smile.
hspace=5 As I surface right next to the boat I pull off my hood, signal OK and let out a cheer.
Then Paul is there with a look of absolute puzzlement asking if I did it. People are yelling on the boats and I am laughing because the minute I have to wait before touching anyone seems like an eternity.
I mockingly fold my arms and roll my eyes at the judge, then tap my fingers on the surface of the water. Finally he tells me that he is satisfied, and the celebrations begin.
Between interviews and photos, delivering champagne to the decompressing divers and visiting the spectator boat, I steal some moments under water alone to reflect on the meaning of it all. Its difficult to explain, but the record is irrelevant. The journey is everything, and its only just beginning.

I would like to thank my amazing team of safety divers, videographers and photographers. They are truly a Dream Team with whom I am privileged to share this achievement. My event sponsors Club Med, the Turks & Caicos Tourism Board and Red Bull believed in free-diving and changed this dive from a dream into a reality. Big Blue Unlimited and O2 Technical Diving on Providenciales provided technical support, staff and absolute professionalism, not to mention a fabulous trip to explore deserted beaches and hidden caves on Middle Caicos. Thanks also to my equipment sponsors Gates Underwater Products, Pelican Rope, Subsalve, Avis and Freediver. Finally, I am honoured to have been able to promote the Whale and Dolphin Conservation Society and the Coral Reef Alliance with this world record. Its my way of thanking the sea. Please always thank the sea - without it our dreams would never come true.