PS: You take a methodical approach to your own training. And recently, you have applied that same approach to revising the traditional approach to freediving safety with DRUMS (Diver Retrieval Unit and Monitoring System). Explain how the DRUMS works.
SM: The diver is connected by means of a lifeline from the wrist to the surface and lanyard to the guideline, in the case of sled diving, at all times. They can be retrieved at any stage during an emergency at an ascent speed of up to ~2.0m/s, depending on the size and weight of the individual and, power of the topside assistant. The system uses a large diameter, custom-made fishing reel and lifeline. It works on a principle similar to deep-sea fishing. There’s no noticeable drag of the line nor is there any tangling. Pre-dive checks of the unit are a ritual; I cannot over stress this point enough.
[“sebastien_murat1” left] During the descent the line feeds out freely. With some skilled handling by the dive supervisor it is quite easy to ‘feel’ for what the diver is doing. In essence, it really is like deep-sea fishing. The specially designed electronic lifeline counter allows us to determine exactly how deep, how long and how fast the diver is moving. With practice it is even possible for the supervisor to establish whether the diver has experienced equalization problems, a blackout or narcosis.
During the ascent the line is slowly reeled in, not so as to aid the diver but only to reel in the slack and ensure there will be no delays in case of an emergency. Of course, during fully assisted variable-weight dives the diver is rapidly retrieved. Control of ascent speed is crucial, especially in the shallow zone where decompression is an issue. The counter is then reset for the next dive at the simple push of a button. The topside supervisor has complete and final control over all phases of the dive such that he may decide, for example, in the interest of safety to abort and retrieve a diver at any time during the dive.
PS: What kind of pre-dive checks do you have to do?
SM: I personally, maintain and check my own gear. Regarding the DRUMS, I ritualistically check it the night before and then again that morning. I check such things as line integrity, reel friction, brake, reel handles, connections, heavy duty velcro wrist cuff, lanyard, reel handle, etc; in short, everything. Paul Murray, the dive coordinator, then runs through his own checks independently.
PS: Is the DRUMS usually mechanized or can it operate by muscle power?
SM: In everything we do we use the KISS method (Keep It Simple Stupid). We’ve found that it was more reliable to use muscle power. Paul’s pretty good for the job of reeling me back in: he’s like Tarzan on Energizer batteries, just keeps on going.
PS: Many have voiced concerns over tangling of the line. How do you prevent tangling?
SM: I’ve never had a tangle; the lifeline is always behind me, dragging. Moreover, it’s some distance from the guidelines. We use two guidelines to prevent ‘spiral wrapping’. Two guidelines keep me pointed in a straight line.
PS: Have you ever had a mishap or accident with the DRUMS?
SM: No. We never foolishly went out and used the rig until I was completely satisfied with it. In the early days, when we were still testing it in the shallows the line would sometimes get tangled as it skipped off the reel and I’d be waiting to be reeled up but nothing. I’d come up and Paul would be cursing with this knotted and tangled line everywhere. It was quite comical.
PS: Did it ever perform below expectations and why? How did you fix it?
SM: I must say that we must of spent countless hours designing and then redesigning the system to cover any scenario before we committed to our first prototype as it was going to be an expensive exercise. We were pleased that the first prototype worked flawlessly straight up with the exception of the odd line entanglement if we let the lifeline spool out freely. We solved that problem by placing guards on each side of the reel, a line guide and an ever so slight bit of friction on the reel during the descent.
PS: Do you believe there would be a role for traditional technical or scuba divers in tandem with DRUMS?
SM: My opinion regarding SCUBA divers is that there is no place for them for deep technical freediving. Maybe they can be used for shallow dives but the problem always comes back to increased logistics, resources and risk. We given it much thought and our view, after many years working in the tourism and pearling industries, is that the risk factor increases in proportion to the number of unknown quantities; each scuba diver is a complex source of unknown and unreliable variables.
PS: How about a lift bag system as a second redundancy?
SM: Once again, we prefer not to use any compressed air of any sort, we find its use an unacceptable source of risk. Instead, as a backup, we use a custom made, variable high-speed winch.
PS: How has using the DRUM changed your freediving?
SM: I use DRUMS to do deep dives on the sled or dives to in excess of 50% of my maximum in fin diving. Basically, with DRUMS I can dive where and when I want, to any depth, doing any discipline and without the chaos of having to a whole bunch of people in the water doing God knows what. Moreover, I can reduce the number of potential risks associated with the dive, all the while increasing the potential performance. Decompression or narcosis related problems, blackouts or the possibility of losing a diver are minimized. The unit is also very flexible in that it can retrieve a diver quickly, in a fully controlled way.
The disadvantage is that I need one trained surface operator to monitor and work the unit whilst Im diving. You also need a platform or boat to attach the unit to but were working on a wet version at present. The electronic monitoring/depth measuring system cost me a bit in time and money since Ive had to design it from scratch. The other thing is that the unit has to be checked every time we go out, but then it only takes a few minutes.
PS: How would you use DRUMS for competitions?
SM: In competition or in training, you could easily set up a few units for people to use in their warm-ups with only one surface assistant per unit. They could dive to any depth they wish, when they wish and without having to retrieve depth tags. We’ve put lot of thought and effort into it and, from a practical/logistical point, it’s as simple as you can make it without resorting to tech divers.
Many thanks to Sebastien Murat for taking the time to explain the DRUMS system and its uses.