Diving to 313m

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I dived in Phuket Thailand 35 miles offshore. The dive site was on the edge of the continental shelf at 450m+ depth. The drop line was weighted and marked every 1m. The tides were right the day of the dive as was the weather. The dive had been aborted previously due to weather (and other less predictable factors). The dive boat and rescue boat were courtesy of ScubaCat (where used to work). The support divers were great again as they were in February when they held me on the line while I convulsed vomiting for 3 hours due to counter diffusion induced DCI. Medical support is great in Phuket with plenty of state run (good, inexpensive) chambers but also a selection of the “usual suspect” private chambers. Phuket treats its divers seriously and you need be never more than 1 hour from a chamber (our rescue boat had 900 petrol horsepower bolted to the back!)

The regulators were chosen for there heavyweight all metal construction helping to maximise internal temperatures. The DFC system is great at managing high gas flows with its smooth operation as opposed to venturi flow support, Finally no environmental seal means less Intermediate pressure amplification with the ensuing high pressure seat instability etc The water temp was 3-4 c at depth, the gas flows were enormous but all resulted in zero free flow or stutter.

"When using twin 20 litre tanks, you have a virtual inexhaustible supply...you can breath again and again."

The descent went very smoothly, the unusual currents would go down, then up, then get weaker then stronger, but mainly because of the slack tide window and neaps dive time, the tides didn’t have a detrimental effect. Once 180m depth came, it brought with it the darkness. Underwater lighting has come along way in the last year and its now possible to virtually guarantee operation to 300m (with the right lights of course!)

My head mounted lights shone onto the down line and every while I would check my depth on the taped measurements against my depth gauges. By 250m I still felt in charge, my lowish helium content added the sort of (two large gins) confidence that would help avoid helium tremors and other HPNS symptoms. The water temperature was chilling, but my dry suit kept the icy water out, I noticed the shakes in my body and hands, but couldn’t really say whether it was the cold externally or internally or helium induced tremors. By 280m I started to grip the line tighter to slow down, I checked my back gas contents gauge and was not impressed by the figure. I had reached my gas turn around pressure by 300m. I didn’t seem overly concerned and this concerned me! I dropped to 310m and looked again at the gauge, 20 bar behind schedule and planned drop time exceeded by one minute. At this time I looked down and saw a ghost like image of some kind of large hydroid, I scanned my eyes from left to right to check for any visual abnormalities and to check the distance more exactly of my jelly like visitor. The little checks I do told me that my concentration was sometimes stalling into a complacent mind lock and this set the narcosis alarm bells ringing. This hydroid looked on coarse to hit my descent line and looked over 2 metres in length!

The Support Team

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I checked the depth on the line, it was deep enough for today. I grabbed the line marker at 313m and headed for 249m the first deeper stop. I shut my eyes and ascended hand over hand, not wanting to see the contents gauge. When using twin 20 litre tanks, you have a virtual inexhaustible supply, even when they equalise with the surrounding water pressure at 26 bar, you simply head up 5m and because of the huge volume, you can breath again and again. (try doing this on twin 12’s near 200m ;-)

The deeper stops came and went without drama, which was not surprising due to the slow ascent rate. The first gas switch was my only concern the rest would be easy. Because of the minimal time at depth, the risk was acceptable. The journey to the first support diver was uneventful (ish), I met Sveinung at 90m and he handed me a 15l of Trimix 14/56. Phil gave me a similar tank at 75m, as did Khun Gai at 60m.

All the subsequent decompression tanks had the same helium content and a falling nitrogen value. By 10metres I had started to detect a shiver in my body, maybe due to the high helium content in my dry suit inflation gas. This dry suit gas helped me avoid skin bends caused again by another kind of counter diffusion. At 9m the long heliox stops began, and this was supplied from the surface through long regulator hoses. A real drama occurred about 2 hours later when the tank I was breathing was changed at the surface. I still had the regulator in place when I felt my tongue get sucked through the second stage and could see the hose collapsing to the surface due to the vacuum! I pulled my now much longer tongue free and cursed the topside monkeys. This was very unpleasant, but could have been much worse. A small communication break down I think!

During the stops, I ate fun size mars bars and banana pieces while the support divers were having their lunch. I knew this was the case because of the chicken bones that were raining down around me. Small fish were closing in all of a sudden, to peck at all the goodies. I hoped a toilet flush wasn’t coming next.

I got out of the water after 6 hours 36 minutes in it. I had got down deeper than any solo diver before me. I had surfaced under my own strength and more importantly without decompression illness. Although I was exhausted I was very happy.