Day 4

Today we were joined by three others (Jeff, an American, John British/New Zealander and Matt, a Canadian) who had done the basic training with Monica during our rest day and when we were doing static apnea with Eusebio. Back in the classroom and a few more videos and then learning about mammalian diving reflex.

The diving mammals, whales, seals, dolphins, etc., have physiological changes when they dive. There is vasoconstriction where the blood vessels contract, increasing the blood pressure; the heartbeat drops dramatically; blood shifts from the extremities to the body core where it is needed more; the spleen contracts to release more red blood cells; the muscles start to work anaerobically (without oxygen from the blood). It was not until recently that this was observed in humans too. There are two things that stimulate it: the face (especially the area around the lips and cheeks) being immersed in water and exposure to pressure while breath-holding.

The first is easy to get to work in your favour. Stick your face in the water with a snorkel but no mask and breathe for five minutes. The second is harder, the only way to get the diving reflex to switch on is to do dives, and the deeper the better. This is a bit of a Catch 22 situation but freedivers have found a way around this by using empty lung dives. You exhale normally and then descend. The way it works is simple: if you exhale leaving only 1/3 of your lung volume and then dive to 10m then your lungs will be crushed to 1/6 of their volume. If you were doing this with full lungs then you would need to dive to 50m to get the same effect. This fools the body into thinking it is being exposed to a much greater pressure than it is.

But there is a price. If you exhale too far and/or dive too deep then the lungs can collapse or suffer adoema, where they flood with fluid to stop them collapsing completely. Either way, you die. It also gets harder to equalise the ears and the mask because there is no spare air. The reward, as we would see later, is worth it when the diving reflex has kicked in. The effect of empty lung dives as a warm up can last for the whole diving day.

Next we worked on our breathing technique. The simple two stage cycle we had been using was no longer adequate and we needed to develop much greater control over our lungs. The first stage is still diaphragm breathing, filling the bottom of the lungs. Next is harder, putting air into the ribs and can be felt by putting the hands either side of the lower ribcage so the finger tips are touching and breathing in such a way that a gap opens up between the fingertips. Third stage is to fill the chest, straightening the back, raising the shoulders and pushing out the chest. When this is full you can still fit a little more air in the back by hunching the shoulders, collapsing the spine and dropping the head -- done right and you can hear the air get sucked in on its own. All of this is done slowly through pursed lips to gauge the flow rate. Eusebio demonstrates it well, his belly popping out like a pregnant woman, his ribs are so flexible that he can grab them and wobble them like they are on dodgy Ikea hinges, his upper body inflating into an unnatural cylinder shape and finally the top of his back bowing out like a hunchback from so much air.

Even though it doesn't feel like it, there is still lots more space that can be used through packing. Packing is sucking air into your mouth at the end and swallowing it into your lungs using the face and throat muscles. You start practicing with a straw, then move on to kissing your finger and then being able to do it free. After five or six packs you feel like your chest is going to explode and Monica & Eusebio didn't recommend it before a dive because so much air can be wasted by escaping through the nose. It now becomes very important to make the pop before exhaling because the drop in blood pressure can really be felt.

In a room of five guys and two girls, it stands to reason that at some point a measuring tape will get produced, the guys will get extremely competitive and the girls will tut, roll their eyes and then sigh. And so it was that Eusebio, like a little boy showing off his favourite toy, produced a mesuring tape and a small, pink balloon with giraffes and dolphins on it (whoever thought that combo up?). Monica, who could communicate an entire conversation with one look, gave him a glare that said, "just for once will you put it away... this has nothing to do with me... it's a boy thing...". Shona gave her a look that said: "me too...".

Eusebio, doing well even though he was so excited, explained how it worked. On the balloon was a line. You take your biggest breath, inhale into the balloon and then measure the line to gauge how big your lungs are becoming. Jeff and Matt both got around 6cm, John and I tied at 7.4cm. Eusebio, packing two or three times, scored 8.4cm. Both Monica and Shona gave us a look that said smugly: "we have nothing to prove...". The testosterone escaping from the room was so strong that three passing Thai women instantly fell pregnant and are now revered as living saints on the island.

Eusebio and Monica went over the new techniques we would need for the final deep freedive tomorrow. The breathe up would be different, this time with three phases: agitation, to warm the lungs up and get the gas interchange working; oxygenation, deep, slow breathing to get the maximum oxygen into the blood; and relaxation, to clear and focus the mind and to rid the body of any excess exertion. Equalisation would be different too, we would still equalise quickly and often at the start of the descent but deeper we would hold it for three seconds each time we equalised. And we would minimise exertion by reaching the breakpoint where the lungs would be crushed so much that they would no longer provide any buoyancy. This would be at around 16m, we would each use a depth gauge with an alarm, when we heard it we would stop finning and let gravity pull us down -- but not to look at the gauge.

In the afternoon we went out on the boat again to practice the cruel and unusual punishment that is empty lung freediving. We started easy, usual breathe up, exhale normally and let yourself sink down the line without finning. As you have very little oxygen in your lungs it is important not to waste any by swimming. The first attempt was horrible, it feels like someone has parked a car on your chest and that you are suffocating. Subsequent attempts become easier though and the big limiting factor on depth is being able to equalise. You can really struggle to get air into your ears. We moved on to duck diving head first, letting your body sink under its own weight, Shona found this quite easy but I struggled to clear my ears after a couple of metres and was stuck with the slower first technique. Most of the first diving session was spent doing empty lung dives until near the end where Monica had us dive normally. The difference was truly amazing, we dropped to around 12-14m with no effort, both of us feeling that we could stay as long as we liked and able to go considerably deeper if we wanted. As a training and warm up technique it is worth the pain.

The boat moved on to another dive site and this time we used monofins for diving. These are huge, equilateral triangles around a metre in length that your feet strap into one of the corners. You swim like a dolphin using only your hips. On the surface they feel terrible, it is impossible to be in the water without a snorkel as your face is always forced down. But dive down and you feel like an animal, moving effortlessly and graceful. "After ten minutes, you will get cramp," warned Eusabio, "well... I don't but you will!" Struggling out the water after exactly ten minutes he was right though.

Monica, not satisfied with torturing us with empty lung dives, showed us another training exercise. Somewhere shallow you dive down, do a handstand on the bottom and fin for as long as you can, counting the kick cycles until you have to come up. Each time you have to do more kick cycles. At the end of it your legs are burning from lactic acid. After that we played in the water, freediving to play with rays and schools of fish that would surround us.

Once again, on an island of all night bars and parties we were ready to collapse at around 8pm.