World Record Deep Wreck Dive

On the 10th of January 2008, my mobile phone buzzed. I was receiving an SMS message. I pushed the button on my phone and read the message: “Pim, would you like to come to the DDE show in Italy in May? Mario”. My friend and (extreme) dive partner Mario invited me to join the Dynamic Dive Exhibition at Lago Maggiore in Italy. I answered: “When I have time, I will be there.” That was the start of a big adventure and a big dive….

The preparation

Marco Braga, program manager of DDE and president of the Italian diving organization PTA (Pure Tech Agency) sent me by email the preliminary program of the show. He was planning to add also some “tech” events. The scope of the tech event was not known yet. But a couple of days later, Marco sent me a video link: the fire department of Verbiana has bought a ROV (Remote Operated Vehicle): a small unmanned submarine, and they discovered and filmed a wreck in (very) deep water. It was the wreck of a ship called the Milano. She lays in a depth of 236 meters. According to Marco that could be a nice subject for a tech diving event: a world record wreck dive (the old record was 205 meters) on Closed Circuit Rebreathers in cold fresh water with three divers at the same time!

Is such a dive feasible? What are the risks? I played with a special version of GAP and with V-planner (dive planing software). I generated some diving and decompression schedules. The outcomes didn’t make me thrilled… long runtimes… high CNS percentages…. Then Mario came up with a dive plan (generated with V-planner B/E conservatism +4) taking into account Open Circuit decompression in a diving bell. Starting at 21 meters on EAN50 and from 12 meters on pure oxygen, generating a total CNS of 23,000%. It would take the bottom divers about 3 hours from the bottom to reach the bell. The deco in the bell would take another 4 to 5 hours. There was room for four divers in the bell, so the team invited also Alessandro Scuotto and Cedric Verdier to take part. 


Over email, we worked on the dive plan (equipment, gasses, emergency procedures, etc.). Fabio Manganelli was the dive marshal and, as such, responsible for the logistics of the dive itself and the Standard Operating Procedures. Every week there was a new version of the SOP document, which was reviewed and commented by the bottom divers, Cedric and Marco. Also, the list with support divers (shallow, deep and very deep) and surface support was completed.

One of the biggest hazards of the dive was hypothermia: the water in Lago Maggiore is 5 degrees Celsius from 30 meters deep. At the surface, the temperature was about 13 degrees. Staying in the water for three hours at 5 degrees is doable. But no longer than that, given the heavy decompression to do. The scrubber duration of the rebreathers is affected by the cold water. Also, the depth of the dive has a negative effect on the scrubber duration (because of the high flow of gas through the breathing loop): so three hours on the canister was the absolute maximum. 

Two weeks before the dive Cedric had to cancel: his diving equipment was stolen when he returned home from a DIR rebreather expedition to the wreck of the Victoria in Lebanon. Now the bottom team comprised three divers: Mario Marconi, Alessandro Scuotto and myself.

One week before the dive, the final version of the SOP was ready. On paper, it all looked like a dive that would be feasible to do. We evaluated all risks and took measures accordingly. But… paper is very patient… reality can and will be different: diving and decompression are not an exact science. How would our bodies and minds react to the great depth, the partial pressures of the gasses, the low temperature? How would our equipment stand the great pressure? Very few or even no data was available to assure a safe dive.


We calculated a bottom time of four minutes and a descent speed of 25 meters per minute: we had to reach the bottom in ten minutes. On a rebreather that is very fast.  (During my descent, my automatic diluent valve (ADV) was constantly injecting gas into the loop. All the time during the descent, I had a pressure alarm on the rebreather. My Ouroboros CCR thought that there was a leak somewhere…).

My personal preparation comprised of taking care of my physical condition (training program and food diet) and making some deep dives (I went with Cedric to the Victoria in Lebanon and dived there on a Megalodon CCR to 142 meters). I was not sure which rebreather I was going to dive on the Milano: the Meg or the Ouroboros.  I prepared both rebreathers and took them to Italy. I was going by car: so no problem of being overweight (when taking a plane). The deep divers prepared their own on board gasses and personal bailout gasses. We decided to carry our own bailout to bring us up to about 135 meters, where the other bailout gasses were staged. The staged bailout gas was calculated for two divers, because the risk of all three divers to bail out was regarded as low. Two days before the dives, I made the decision to dive the Ouroboros. The reasons were the fact that Mario and Alessandro were also diving a Boris, the fact that the Boris has a radial scrubber and the (first stage) regulators were extreme regulators (certified for great depths). And for the Meg it is advised to fill the handsets with mineral oil when making extreme dives.

There was still another thing to do: ask permission from my insurance company (DAN Europe) for the dive. I send them an email explaining the dive and the standard operating procedures . DAN indicated the dive was high risk and on the border of what is regarded as physically and humanly possible. They stressed the risks of hypothermia, oxygen toxicity and also HPNS (High Pressure Nervous Syndrome).  After some email discussions, I got the approval from DAN Europe to make the dive.

I didn’t talk a lot about my plans to make a world record dive. However, I talked about it to some students. One of them was Remko van de Peppel. He offered to join me and act as my personal shallow support diver. I gratefully accepted his offer. On the 6th of may we got into my van and drove the 1250 kilometers down from The Netherlands, through Germany and Switzerland, to Italy, fully loaded with technical diving gear. Late in the evening we arrived in our hotel In Verbiana, looking out over Lago Maggiore.


The dive

The 7th of May early in the morning, Remko and I went to the harbor of Verbiana. There we met with Fabio, the Dive marshal. A large pontoon was already in the water. The bell would arrive that day. A vessel with a crane on the deck from the sponsoring diving company Palumbarus would put the bell in place. The bell was bright new and had to be fitted with all the hoses for the gasses, communication system and warm water. Alessandro was taking the lead for fixing the bell. We underestimated the job that needed to be done on the bell: it took one day more than expected. And because we wanted to test the bell properly, we postponed the date of the dive one day. The bell was suspended under the pontoon so it could not be lifted out of the water. That meant that we had to exit the bell through the water. Because of the risk of oxygen convulsions, it was decided that the deep divers would exit the bell on open circuit, using full face masks. 

On the 9th, the pontoon was towed to the location of the wreck. The wreck had been located the day before by the fire department and a shot line has been put into place. With the help of the ROV, the shot was placed 30 centimeters from the wreck. Next to the shot a deco station was put into the water, which started at 80 meters. On the deco station also the bailout gas was staged. I made a quick dive to 60 meters along the shot to test my descent speed, check the visibility and the water temperature. The tests of the bell showed the bell was working perfectly. 

In the evening, the entire team assembled in the harbor for the final big briefing. Laminated task lists and decompression tables were distributed amongst the team members. After the briefing, I went to bed for a brief night…


At 6 AM, we got up and went to the harbor. In the harbor, I had a light breakfast and tried to clear my mind. At 7 AM we went on board of the vessel which would take us to the pontoon. We would gear up on the vessel and go into the water from the vessel: the pontoon was about two meters above the water. I did my usual rebreather checks. Mario, Alessandro and I had a short last talk: when during the ascent one diver had to abort, the other two divers would continue the dive. When one diver has to abort the dive on the bottom, all three divers would ascent together. At 8.30 AM, we were ready to enter the water. The swim to the shot was a short one. At the shot, we got our video cameras. We made the last OK sign, and we started the descent.

I was letting the rope of the shot slide through my fingers. It made a sizzling noise. In the meanwhile, my ADV was inflating the loop continuously . I was continuously inflating my drysuit and adding gas to my BCD. I passed two shallow support divers who were checking the deco station. Suddenly at 140 meters I got a low pressure alarm: my on board 2 liter diluent tank was almost empty! So I switched on my off board diluent and I continued my descent: still 100 meters to go. I also switched to my high setpoint (1,5). Switching earlier to the high setpoint would have caused spikes in the PO2.

At 220 meters, I saw a dim light coming from the bottom: the ROV was illuminating the wreck. I didn’t wear a helmet like Alessandro and Mario. I only carried a Metal sub LED light. Mario and Alessandro were swimming around the ROV and the wreck. They both signaled that they were OK. I took my video camera and taped them. I was touching the bottom and took some images of the two divers from below. At 14 minutes runtime, the three of us started the ascent. The ascent speed was relatively high until 150 meters. From 150 meters up, the ascent speed was the “normal” 10 meters per minute. I was feeling good and very pleased with the new world record. The only thing left was a long deco of almost eight hours… But then at 120 meters, I felt water coming in into my drysuit. I immediately felt the cold through my body. I was suspecting a leak on my OPV (over pressure valve). Later (after the dive) I discovered that the membrane of the OPV had shifted. It went through my mind that it would be a tough ride to the surface. Meanwhile, however, I shot some film of the divers and also of the deep support divers at 100 meters. We were signaling them from below that we were OK and that we were coming up. It always feels good to know that support is close. I indicated I was getting pretty cold… and heavy. My drysuit got really flooded. I used a lot of argon and diluent. Around 80 meters, we went off the shot to the deco station. There I saw Alessandro was having problems. Mario was already assisting him. At a depth of 60 meters, Alessandro had to bail out. He stayed on open circuit until the bell. I was getting more and more cold. My sight turned bad: I had difficulties to read my decompression tables. My fingers felt numb and pressing inflators and holding onto the deco station was getting difficult. At 40 meters I met Remko. Meanwhile I ran out of Argon, with still one hour to go before entering the bell. I told myself to hold on for another thirty minutes: I skipped thirty minutes to enter the bell earlier. I decided to compensate the skipped in water decompression time when I was in the bell. 

Remko accompanied me to the bell. Together with another shallow support diver, he took off my Ouroboros. I could barely move. I was trying to get into the bell, but almost every power has left my body. Only when Remko signaled that the other divers needed to enter the bell, I could push myself inside. In the bell, I opened the oxygen valves and put on a breathing mask. I felt very dizzy and had to vomit once. Ten minutes later, Alessandro and Mario were entering the bell. Alessandro was not in a good shape and he vomited frequently. Every thirty minutes we did our air breaks and after a while the bell moved up to the next deco level. After almost five hours, I was going to be the first diver to exit the bell. I putted on a rec BCD with Full Face Mask. Two fire department divers guided me to the surface.  There, a large crowd was waiting for me. Surface support laid me down on the warm deck of the vessel. My wet suit was removed, and a medic checked my blood pressure and did some “sanity” tests. I was feeling pretty dizzy and getting up on my feet was difficult. I was wrapped up in an aluminum blanket to prevent the loss of body heat. Cameras were clicking and zooming. TV teams from Italy, Russia, US and South-Africa were filming the entire event. With a couple of minutes interval, Alessandro and Mario emerged. Alessandro was taken care of immediately by the medics. In spite of his physical condition, he was smiling and waving to the crowd. He was put on transportation to the nearest decompression chamber. Mario and I gave some interviews and posed for pictures. Slowly, the people were leaving the vessel and the pontoon. Mario and I were transported back to the harbor… We had a lot to talk about, but we saved it for later. It took me another two days before my dizziness had disappeared completely.

World Record Wreck Dive 2008
World record wreck dive made on the Milano wreck on 236 mtrs in Lago Maggiore (Italy) on May 10th 2008 by Mario Marconi, Alessandro Scuotto and Pim van der Horst during the Dynamic Dive Exhibition 2008 (on Ouroboros CCR)

Pim van der Horst

Pim started diving in 1983 at the University of Tilburg (The Netherlands). He came in contact with technical diving when nitrox was introduced in The Netherlands in the early nineties. A next step was rebreather diving. He had to seek technical training abroad (UK and the US). Technical diving and especially rebreather diving got the interest of Pim and he continued his technical training. He started up his own technical diving school in The Netherlands: Pim’s Tekdiving (PTD). PTD has several facilities in The Netherlands and instructors abroad. Pim is Tri-Mix Instructor Trainer Closed Circuit (more then 10 different rebreathers) and Open Circuit for several agencies (DIRrebreather, ANDI, IANTD, PADI, PTA/CMAS and WOSD). Pim trained over a 1000 divers. Pim publishes on a regular basis in Dutch and Russian diving magazines. He is the author of several books on technical diving and rebreathers. Contact:


Mario Marconi

Mario began his diving activities in 1993. In 1997 he has accomplished his first diving training with IANTD. In 2001 he became a PSA Advanced Deep Air Instructor and then started with his deep caves explorations, with open circuit first and then moving to closed circuit. He is also using and studying the advantages of Heliox diluents for closed circuit deep cave exploration. In 2002 he co-developed and tested the SCR Passive addiction EDI2002 specially projected for cave dives in extreme conditions. Mario is a P.T.A./C.M.A.S Extended Technical Instructor, Full Cave Instructor Trainer and Ouroboros Rebreather Instructor. Contact: 


Alessandro Scuotto

Alessandro had his first dive at 6 years old, and his first scuba certification at 12. At 18 years old, he already was a recreational diving instructor. In 1996, he had his military underwater certification with “Com.Sub.In” from the Italian Navy. In 1997, he achieved his first technical instructor certification. Using Rebreather from the very beginning, he experienced lots of hours on different machines. Next to that Alessandro is an OTS (Commercial Diver), Hyperbaric Chamber Operator, R.O.V. pilot, UW submarine pilot. Now he is the vice chief of Napoli’s section of the underwater team of the Italian Police. He is also the chief executive officer of Deep Sea Technology (commercial diving company). Alessandro is Instructor Trainer for PTA/CMAS, NASE and PSA. Contact: