Strap Those Twins On Me

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May 23rd 2007
Published: August 6th 2007
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Mat: After Jeremy and I finished our southern Laos trip, Trace and I were at a bit of a loose end. We had not really planned anything for our last 5 weeks in Asia. I was interested in heading to Indonesia, Trace was keen to try a couple of courses in Thailand (cooking, yoga, meditation, underwater videography, or a divemaster course). Jeremy had left to go to Koh Tao in Thailand to do a technical diving course, but we needed to stay in Vientiane to pick up some of our gear that was arriving on a bus from Vietnam.

In the end the gear arrived quickly and we were in Bangkok only a day after Jeremy. The diving course Jeremy was starting involved deep “technical” diving with twin back tanks, and two decompression tanks with higher levels of oxygen to speed up the decompression process. His instructor Jamie was the guy who owned the dive center I did my divemaster with in 2003, so I knew him well. After an email from Jeremy and Jamie I was convinced (with a huge twist of my arm…) to come down for the course, as it involved a three day live-aboard trip to the “Pangan” a lovely Japanese-built wreck 10 hours north of Koh Tao, and was well discounted due to the fact I had done a more basic decompression diving course in New Zealand the year before. It also fitted in with what Trace wanted to do as far as doing her divemaster or other courses.

So, without even spending a night in Bangkok, we left on an overnight bus then boat to Koh Tao. The strong suction force of Koh Tao had worked its magic again. In the end we did not leave the island (apart from a visa run to Burma to get another 30 days in Thailand) until three days after our scheduled flight to London…

On arrival at Koh Tao I was straight into the tech diving course. Jamie strapped some twins on me (twin scuba tanks, not women), and we headed out so he could check I was comfortable and capable of handling the gear, doing a few of the necessary drills, sending surface marker buoys to the surface, and so on. The next couple of days involved academic study and further training dives to refine the skills necessary for the demanding nature of the diving we would be doing. An example of the drills is a gas shutdown drill, where Jamie would simulate one of our regulators free-flowing. We then needed to shut the appropriate valves on the twins behind our head and swap regulators if necessary, all within a certain time and while maintaining neutral buoyancy.

After a few days of the initial training we headed out to the Pangan to complete the final three training dives of our course, then three fun dives. The Pangan was a Thai Navy vessel that was a gift from the Japanese before WWII. She lies in 60m of water, and we were planning 25-minute bottom times on her.

To give you an idea of what is involved when diving to these depths, here follows a brief attempt at diving theory.

For every 10 meters you descend underwater there is an additional atmosphere of pressure on your body (so at 60m there is 7 times the pressure on your body compared to at the surface). Because we are mostly water (which is incompressible) the only thing that you notice as you descend is increased pressure on your eardrums. The pressure on your lungs is not noticed as the scuba gear is ramming more air into your lungs to compensate exactly for the increased pressure of the surrounding water. As a result, the air in your lungs takes up the same space but is more dense (so at 60m you have 7 times the amount of air in your lungs as at the surface, but it is still just a lungful to you). The main effects of this are:
• You use more air the deeper you go (at 60m a scuba tank will last 1/7th the time it would at the surface).
• The increased amount of nitrogen in your lungs is absorbed by all tissues in your body. This happens with all scuba diving, but is far more of an issue during deeper and longer dives. If after absorbing this nitrogen you ascend to the surface too quickly you bubble like an opened beer. This is not good.
• The increased pressure of nitrogen and oxygen has a noticeable narcotic effect after 30m or so. One analogy for this states that at 30m the narcosis it is equivalent to knocking back one martini, then another for every 10m you descend. At 60m things are far more enjoyable and wondrous than at 20m, but you are somewhat retarded which can be a problem if important decisions need to be made quickly.
• At increased pressures oxygen is toxic, and can cause seizures without warning. If relatively relaxed, this should not be an issue at 65m, but add physical exertion and anxiety, and it could be. A seizure is not a problem in itself, but if it occurs while you are underwater, you drown.

So, if you dive to 60m for 25 minutes you need to take lots of air to breathe, you need to be comfortable with the narcosis, and you need to take 80 minutes to slowly come to the surface. This 80 minutes “decompression” can be sped up by breathing gases with an increased proportion of oxygen (normal air is roughly 21% oxygen, 79% nitrogen). The higher the oxygen content, the higher the rate at which you get rid of the nitrogen you absorbed at depth.

The only problem with this is that you can not breathe oxygen enriched air (nitrox) at depth because of the toxic effect mentioned above. The higher the oxygen content, the shallower you need to be before it can be breathed safely. Pure oxygen can only be breathed safely at 6m.

Sooo, for these reasons, on a dive to 60m for 25 minutes we took two 11L back tanks (twins) of air for our bottom gas, a tank of 36% nitrox for deco shallower than 33m, and a tank of pure oxygen for deco shallower than 6m. This cut down on the deco time from 80 minutes to 40 minutes.

It is hard to describe how fantastic the diving was during the three days on the Pangan. It was very rewarding for a number of reasons. For one, intentionally getting yourself into a lot of trouble with regard to absorbed nitrogen, then getting yourself out of trouble is a buzz. At our first deco stop at 30m or so we could look up and see the boat floating lazily on the surface. At this stage I knew if I went to the surface then I would mess myself up or possibly die. So surfacing after the required deco feeling good makes you feel alive.

Another aspect that made this diving so great, is that we were diving on a wreck that only a few people have seen since it went down. A wreck like the Rainbow Warrior, which has been sunk as an artificial reef, is good fun, and beautiful, but a real wreck in deep water is as good as traveling back in time. There is the obvious decay and marine growth, but it is as if time has been frozen.

The grand beauty of a decaying steel ship as you swim through it, with deep blue shafts of light penetrating its dark innards has to be experienced to be understood. You also share the dive with a variety of underwater life. A massive grouper might be hovering in the gloom just under the bow of the ship, or a multitude of soft corals may provide a colourful swaying new surface for the ship in contrast to the rusting metal below. The experience is exaggerated by the narcosis, if it wasn’t for the reg in my mouth I would have been smiling like a Cheshire cat the whole time.

We were diving from the M.V. Trident, which was perfect for the trip. Jamie and his mate Stewart had purchased the boat two years ago and have spent the intervening time using it to find new wrecks in the Gulf of Thailand. They are the only guys really doing this, so any wrecks they find are virgin. In 2005 they found the “USS Lagarto” a WWII US submarine sunk in 1945 by a Japanese destroyer. It still has 86 crewmen aboard and lies in 73m of water. If anyone is interested check out Jamie, Stewart, and the Trident at:

Back on Koh Tao, Trace had done nitrox and “deep” diving courses in an attempt to keep up with the boys, and had also tracked down an Irish videographer (Alan) who was going to teach her underwater videography and editing for three weeks for $800. After agreeing that the suction forces of Koh Tao were too strong for us to resist, Trace started the videography course and I booked on a trip on the Trident to dive the USS Lagarto.

After a week relaxing while Trace was diving, editing, and getting personal Muay Thai instruction (Thai kickboxing), I got itchy feet and after doing a border run to Burma with Trace headed south from the Burmese border to Kao Sok national park, and spent a couple of days there. The scenery on the lake I stayed on was spectacular, with large karst peaks rising from the lake much like a fresh-water Halong Bay. In the national park we saw quite a bit of wildlife, including gibbons, hornbills, and I just about stood on a python in a limestone cave as we wound our way through the solid rock for an hour. (Eight people, including four Swiss, a Briton, a 10-year-old German boy, and their Thai guide drowned when a flash flood trapped them in this cave in October 2007 - five months after I was there).

After a week away from Koh Tao it was good to be back, and I went with Trace on a couple of dives to our favourite dive site as she took video. The next day Jeremy joined us and Trace got some great footage. The edited version is a fantastic memoir of our time on KT. It is impressive how much Trace learned in three weeks.

Before we knew it the time came for us to board the Trident for the Lagarto trip. Jamie had kindly said Trace could come along for the eight days. This was very thoughtful of him, considering that women are usually discouraged from coming on tech dive trips (unless they are diving). Her acceptance onto the man-boat may have had something to do with her swimming in her bikini above us decompressing boys on a day trip to a small wreck close to Koh Tao…

After a night on Koh Samui (and a crazy 10 minutes on go-carts that went 90km/hr) we picked up the well known wreck diver John Chatterton ( from the airport. John hosts the TV documentary series “Deep Sea Detectives” and made headlines around the world when he found and identified a mystery WWII German U-boat off the New Jersey coast in the 90s. The fascinating book “Shadow Divers” tells the story of the U-boat’s discovery and identification. Once John was onboard we headed towards the south of the Gulf of Thailand and our first wreck.

The first wreck we were diving on was a large freighter in 60m of water. Jamie and Stewart had not managed to identify the wreck during previous dives on her, but after two dives John had found the name “Solimoes” in 70cm steel letters on the bow! Sounds easy, and we gave Jamie a bit of stick for not finding them previously, but the letters were covered by marine growth and soft corals. To find them John had run his knife down the ship in an area he figured a name should be, and hit the letters.

We spent two days on the Solimoes before traveling to the Lagarto. These dives were to be our deepest ever dives. On the morning of our first day over the Lagarto, Jeremy and I descended with a mixture excitement and sensible apprehension from the calm warm surface water, down down down along the descent line towards the sub. As usual the first 40m or so was very clear, but the visibility deteriorated as we hit the thermocline (a line where there is a change in water temperature). The viz at this point was only 3m or so, so when the top of the conning tower suddenly appeared from the gloom it blew me away. Here was an American submarine that had been sunk 60 years before. We spent the 20 minutes of this dive lazily circling the conning tower and its base at 65m, enjoying the combination of narcosis and A BLOODY HUGE WWII SUBMARINE!

One of the more interesting things around the conning tower was the “TBD” (target bearing device). This consisted of a brass binocular-type device with two large side handles. At the time of the sub’s sinking it was a state of the art piece of equipment used to help guide the firing of torpedoes. One of the crew would stand on the deck and follow a moving target with the TBD. The movement of the TBD was feed to a computer the size of a fridge in the sub, and this in turn would churn out data that was used to direct the torpedo. Cutting edge stuff.

For our next dive we wanted to visit the damage on the port side of the submarine that was caused by the depth charge that likely sunk the sub. This however was about 70m deep and pushing the boundaries of what is considered safe for oxygen toxicity, not to mention an increase in the narcosis load again. To reduce this risk we added helium to our back gas for the second and third dives (trimix 17/20 - 17% Oxygen, 20% Helium, 63% nitrogen). This brought the oxygen toxicity risk within acceptable limits, and reduced the narcosis to the equivalent of about 55m. The main complication of diving with helium is that it is absorbed by the body quicker than nitrogen, so decompression needs to be longer and start deeper. As a result our first decompression stop was at 45m, and then every 3m after that to the surface. Quite entertaining considering that the absolute limit for recreational diving is 40m.

So the second dive saw us head deeper than we had ever been in order to explore the depth-charge damage. We had been told that if we headed to the forward gun and then dropped down on the port side, we could not miss the caved-in side of the sub. After investigating the forward gun and the large snapper that was hovering over the barrel, we dropped down to find the damage. We could not have missed it. An area 5m high and 3m wide was caved in. The thick steel submarine casing was ripped open like tin foil, and the hugely robust inner pressure hull was pushed in and around one of the internal decks. The men that had been near the explosion point would most likely have been killed instantly, and even those at the other end of the submarine would have been knocked unconscious by the percussive shock of the blast. It gave me a chill thinking of being inside the sub during the attack.

From the damaged area we ascended slightly and headed forward towards the bow. It was here that we came across the dive planes - huge horizontal slabs of steel used to control the sub’s diving. The dive planes were still at an extreme dive angle, likely frozen in time from the moment of the depth-charge impact. The divers that had been to the stern of the sub reported that the rear dive planes were also in full dive position, and the rudders were hard to port. So the most likely scenario before the sinking of the sub was that it was performing an extreme evasive maneuver, diving and turning to port as quickly as possible. Unluckily the sub probably turned into the path of a depth-charge and suffered the catastrophic damage.

Despite the extent of the damage from the depth-charge, it does not seem that the pressure hull is breached. So it is unclear what caused the sub to fail to recover from the blast. On our third dive we could see one possible reason for a flooding of the sub. On the forward starboard side one of the torpedo tubes is half open. After his first visit to the sub John Chatterton hypothesized that torpedoes had been fired from the Lagarto in an attempt to sink its attacker. These may have missed their target, and during the subsequent evasive diving maneuver, the crew would have been hurriedly closing the torpedo doors. At the time of the blast one of the doors was still in the process of being fully closed, and the shockwave from the blast could have traveled down the torpedo tube and blasted open the inner torpedo door (which is not as strong as the outer door, and opens inwards rather than outwards). This would have caused a rapid flooding of the bow of the sub, closely followed by flooding of the rest of the ship.

In order to investigate if the inner torpedo tube door had been blown open, John had brought an ROV small enough to fit into the torpedo tube. While he preparing the ROV we where finishing off our amazing third dive. We visited the open torpedo tube before dropping down to the sand and moving to the very bow of the sub. Hovering over the sand at 73m looking up at the dark silhouette of a huge WWII submarine’s bow rising up above us was jaw-dropping.

Back aboard the Trident saw us assisting John to prepare to ROV for the exploratory dive. The main logistical issue was ensuring the small ROV could tow the 90m of umbilical cord through the current before arriving at the torpedo tube. After discussing a few possible techniques for achieving this, common sense prevailed and two divers led the ROV like a small yellow underwater dog to the torpedo entrance before letting it go and allowing John to maneuver it into the tube. After some remote-controlled deep-water wriggling he was inside, and slowly moved down the tube, keeping hard against the tube roof to avoid stirring the silt.

The anticipation of everyone watching the ROV control screen was palpable. We knew that within a minute we would have an answer as to whether an open torpedo tube played a part in the sinking of the Lagarto. I wish that all surface intervals were as interesting as this one! Then moment of truth arrived. Slowly the inner torpedo tube door came into view, it was tightly shut.

One possible reason for the Lagarto not recovering from the blast had been ruled out. We may never know the exact circumstances of her last minutes. Possibly the incredible violence of the depth-charge explosion caused wide-spread failure of many of the mechanical and electrical components of the submarine. Almost certainly there would have been countless leaks all over the ship. This, combined with the incapacitation of most of the crew, may have meant that the Lagarto could not recover from the blast.

The Lagarto is now a war grave. The Trident is the only boat permitted to dive near the site. Those diving on the Lagarto treat the site with the utmost respect, and nothing has been removed from the sub, and there will never be any penetration of the hull by divers. A US flag attached to the conning tower during a memorial service two years prior still flies in the current over the Lagarto and the 86 submariners still inside.

After four dives on the Lagarto we sailed west towards the “Seacrest”, a drilling ship that sunk in a typhoon in 1989 with the loss of 91 crew. On the way to the Seacrest we stopped to check out a mark Jamie had from Thai fishermen. As with most wreck hunters, Jamie and Stewart have found their wrecks by combining research with the co-ordinates of good fishing spots from fishermen. In particular, the sites where nets have been lost are of interest.

After “mowing the lawn” around the fisherman’s co-ordinates a solid hit sprung up on the depth sounder, and a shot-line was dropped. Stewart headed down to tie off, but unfortunately the wreck was just a steel barge, rather than an ancient Chinese junk or the like. You can not win them all.

Over the next two days we dived on the Seacrest, which at 50m to the sand was shallower than the other wrecks. Trace even went for a dive with our new French mate “Silty” Laurant (so called because he was always penetrating into tight silty areas deep in the wrecks and sending billows of silt out of every nearby opening). Jeremy and I felt quite silly with our four tanks and tech kit, while Trace swam past in her fluro-yellow shortie wetsuit and single tank on a quick dive to 45m. Classic.

Once we arrived back on Koh Tao we had two days to get our fill of Thai food and beach life, before heading to Bangkok for our flight to London (which we had put back a few days due to the Lagarto trip). After buying some good imitation jeans, a fake student ID card, some pirated computer software, and some glasses and contacts for Trace we were on the plane.

Leaving Bangkok meant that we were further from New Zealand than we had ever been. Looking down and seeing the landscapes of Burma, India, Pakistan, Afghanistan, and Europe was great. For some reason we also did a low circuit over London which allowed us our first glimpse of some famous landmarks. On landing we headed for the tube and disembarked 10 minutes walk from our friend Jesse’s place. London is obviously a change after 6 months in Asia. Things that have struck us in the first few days are: 1) it is cold, despite the fact it is meant to be the start of summer, 2) its orderly and clean, 3) there is fantastic information all over the place (for example a hole in the road was blocked off with orange fencing and there was a professionally printed information board explaining the importance of restoring the Victorian water pipes), 4) it is expensive (converting prices to New Zealand dollars, let alone Thai baht is a scary process).

We are broke, but happy, and have had an amazing 6 months. After finding some work we will check out the UK and as many parts of Europe as we can. Bring it on!

Additional photos below
Photos: 55, Displayed: 37


6th June 2007

Gore(not Al) blimey limey London. What a weird on wasnt keen myself and legged it to Edinburugh asap have a guiness in the pub and pay respect to the jacket,All blacks, The cups( yatching?) are heading home and the Rig/Rabbit who are having a mullet disguised as a baby soon. if u see the Queen pash her for me and the her dogs rock...... Gotta blow me olds mates....shinner china dog and bone me Dog woof woof
10th June 2007

good luck!
Hi Tracey, this is Tim from NZ - have enjoyed all your photos from your trip so far: some very nice compositions! Well done to you both! Enjoy the next phase of the journey!
6th February 2015


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