What It's Like to Freedive to 56 Meters (183ft)
At the AIDA World Championships in the Bahamas over the past couple weeks, I've had an unparalleled opportunity to train and refine my freediving technique, culminating in a 56-meter dive to open the final day of competition. The dive was straight down a line to a target, and back up, wearing a monofin, on one breath, with no other assistance. I'd like to describe what went into a dive like this, and how it felt. (Incidentally, the pictures are not of me, except for the last one.)
I arrived at Dean's Blue Hole about an hour in advance of my dive, and was in the water by the platform with about 20 minutes to go. The key to freediving is relaxation, and I was feeling a bit rushed and nervous, so I started by removing my mask, putting on a noseclip to prevent water getting up my nose, and breathing face-down through a snorkel for a few minutes. Semi-deep inhalation, pause, exhale slowly for ten seconds, pause, repeat. The slow exhalations slow the heart rate, and the water on the face starts to kick in the diving reflexes.
After the facial immersion, I put my mask back on, took a deep breath, and pulled slowly down the warmup line to about 10 meters (33ft). After about a minute my diaphragm started to contract on its own, an involuntary reflex; slightly uncomfortable, but you get used to it. The pulse decreases as the diving reflex gets stronger, the spleen contracts to release oxygen-carrying red blood cells into my bloodstream, and I let this happen for another minute before pulling slowly back up the line to the surface.
A couple minutes recovery, then a "negative pressure" pulldown; I took a deep breath at the surface, then exhaled to a comfortable level, and pulled back down to 10 meters. With two atmospheres of pressure on me, my chest and lungs were compressed to simulate a deep dive, deeper than the one I was about to make. The feeling is like a bear hug, unusual but not uncomfortable. Pull back up to the surface, inhale, relax. Seven minutes to go.
I move slowly over to the main "competition" line, which is rigged with a heavy counterballast and sailing clutches, allowing the safety team to quickly lift me to the surface in case of emergency. At the bottom of the line is a white target plate, with several velcro tags attached; the diver must retrieve a tag from the plate to demonstrate that he/she made the depth. Below the plate is a light, and a video camera. The line is taut and inflexible,with marks every meter along its length. For this competition, the line also glows in the dark, useful at depths below 40 meters where not much light penetrates. The line is dropped to 56 meters for my dive, and I clip a meter-length (3-foot) safety lanyard to my left wrist, with the other end clipped to the line. This way I can swim with my eyes closed, without the risk of drifting off into the ocean.
As the minutes count down, I lie on my back, with my right arm holding the line, and my neck supported by an inflatable neck pillow. I'm wearing a 3-millimeter wetsuit with a hood, a 5lb (2.2kg) neckweight, and a wide-blade monofin, with both feet securely strapped in. Breathe in, pause, slow exhalation for ten seconds, pause, repeat. I lift the skirt of my mask and sniff in, bringing fresh air into the mask, then make sure the mask is sealed properly against my face. Eyes closed, focusing on my breathing. The hood of my wetsuit drowns out the noise of fifty spectators, and my coach DeeDee relays the official countdown in my ear: Three minutes, two minutes, one thirty, one minute.
At thirty seconds I change my breathing style to a faster exhalation, about four seconds, and a deeper inhalation. This clears CO2 out of my system, which will make for a more comfortable dive, and less urge to breathe. It also fills my lungs with nearly 21% oxygen, as opposed to the 18% oxygen / 3% CO2 mix that fills the lungs with normal shallow breathing.
Twenty seconds, ten seconds, five, four, three, two, one, "official top". I now have a thirty-second window to start my dive. I take a couple relaxed breaths, then a very full inhale: diaphragm, chest, shoulders, neck tilted back, about 7.5 liters. Then I "pack" more air by taking mouthfuls of air and pushing it into my lungs; about twenty-five mouthfuls in ten seconds, adding an extra liter and a half to my lung volume. I reach my left arm across my body towards the line, which rolls me over face-down in the water. Duck my head straight down, lift my monofin in the air, and sink vertically into the water.
Near the surface I am quite positively buoyant, from all the air in my neoprene wetsuit and lungs. So once my fin is in the water, I make two or three medium-hard kicks, down to about five meters (15ft). My left arm is raised above my head, pointing straight down, and my right arm is tucked in, holding my nose to equalize my ears. Kick, equalize, kick, equalize, kick, equalize. The equalizations are done using mouth and throat muscles only, not with the diaphragm. I keep my legs straight and use my entire body to kick, smoothly gliding in curves through the water. Every few equalizations I add some air through my nose to my mask, as the increasing pressure causes it to be drawn tighter against my face.
At ten meters I am much less buoyant, as the pressure has compressed my air in half since the surface, feeling like a normal shallow inhale. My kicks get softer: kick, equalize, kick, equalize, kick, equalize. I am dropping at a rate of about a meter per second. By twenty meters, the pressure has tripled since the surface; my lungs now feel like a normal exhale. My depth notify alarm on my gauge goes off; time for a mouthfill. I exhale from my lungs, filling my mask and cheeks as much as I can, then close off my throat to prevent the air from being drawn back into my lungs, which are now at negative pressure. I am still feeling a bit tingly from my low carbon dioxide level, and I have absolutely no urge to breathe. I pinch my nose and compress my mouth and throat, allowing a near-continuous equalization as I descend, continuing to softly kick. My buoyancy is now neutral or slightly negative, as the air volume continues to be compressed.
At thirty meters, I enter the most enjoyable part of the dive: sink phase. With negative buoyancy, I can sink without kicking, so I let my body relax, vertical and streamlined, with my left hand using the line as a guide, right hand still on my nose for equalizing. As the air in my mouth compresses, I replenish it from my lungs by using my tracheal muscles to force up air, until the negative pressure prevents me from doing so. At around forty meters I do a final mouthfill, using my diaphragm to get that last bit of air into my mouth and cheeks. I tuck my chin to my chest, minimizing the airspace in my trachea, using the remaining air for equalization.
My lungs are now at significant negative pressure, and the diving reflex is kicking in strongly. My pulse drops into the forties or thirties, and I focus on keeping my throat locked off, equalizing using the remaining air in my mouth. Equalize, sniff in a little air from my mask, equalize, sniff, equalize. The mask gets tighter around my face. On the surface platform, I am visible on sonar, dropping. The competition organizer, Sebastian Naslund, is tracking and relaying my progress to the crowd: "Forty meters, going down. Forty-five meters." The judges at the surface are in the water holding the line, feeling the slight vibrations of my lanyard clip against the line as it descends, waiting for the pull to signal my turn. At forty-eight meters my second depth alarm goes off; eight meters to go. I am sinking fast now, eyes closed. Equalize, sniff, equalize, pressure on the chest, sinking down, down, down.
Bam, my left hand hits the mark: a tennis ball on the line about a meter from the plate. Elapsed time since the start of the dive: just over one minute. I open my eyes, grab the line with my left hand, and reach down with my right hand to tap the plate. The tags are reserved for the actual competitors, so I don't grab one. The artificial light makes the water a glowing medium blue; it feels shallow, even though very little ambient light penetrates this deep. My chest is tightly compressed from nearly seven atmospheres of pressure, though I still feel zero urge to breathe. The partial pressure of oxygen in my lungs is well over one atmosphere; I could stay conscious at this depth for quite a long time, though the nitrogen and CO2 narcosis soon start to kick in. Focused on my task for the moment, I don't feel it at all. My body sinks to the plate level and I reverse direction; grabbing the line with both hands, pull strongly, starting my ascent.
The ascent is simpler than the descent, because there's no need to equalize. I raise both hands above my head to streamline my form. Ten medium-hard kicks off the plate, and I am at forty-five meters. Further from the plate, the surrounding water gets darker. Twenty kicks, thirty-five meters. I am entering the most difficult phase of the dive, because carbon dioxide building up in my system is triggering an urge to breathe, and the pressure still gives the sensation of empty lungs. But there is no panic; I'm doing exactly what I need to get back to the surface, and the safety divers are waiting.
Kick, kick, kick. My mask is expanding as the pressure drops, I can sniff in some fresh air and inhale it; aahhh. Twenty five meters, twenty meters, the water is getting lighter. The safety diver appears, swimming in front of me, watching, making sure I'm ok. I sniff in more air; my lungs are expanding, it feels like I'm inhaling. The dive is getting easier. Kick, kick. The second safety diver is there; the kicking get softer as my buoyancy lifts me towards the surface. Slight leg burn from lactic acid, but not bad.
At ten meters the safety diver drops his arms; that's my cue. I stop kicking and make a swimming stroke with my arms, propelling me towards the surface. I glance up to check my depth. At five meters I begin to exhale, avoiding lung overexpansion at the surface, preparing to take a full breath of fresh air. Nearly there. Three, two one; break the surface. My hand is on the line, I grab it and hold on. Elapsed time: one minute fifty seconds. Full inhale, hold for a couple seconds, pressurizing my chest to keep the blood pressure up, staying awake. Quick exhale and another inhale, hold, pressurize. Exhale-inhale, hold, pressurize. Breathe, breathe, breathe. Feeling fine. I take off my mask, face the judges, give an ok hand signal, and say, "I'm ok." Then wait thirty seconds. The judges give me a white card: clean dive to 56 meters. A new personal best!!
To put this in perspective, the world record is more than twice as deep: Martin Stepanek recently dived to 122 meters and back, with a total dive time of 3:36. But I'm thrilled to say I've dived a quarter a way to the bottom of the Blue Hole. Eleven more meters, and I'll be a third of the way down. Perhaps next year? The deep is calling...