I booked onto the Advanced Recreational Trimix (ART) course at Vobster Quay on the spur of the moment, but I have been looking to add skills in this range to my repertoire for a little while now, as a lot of UK diving involves wrecks in the 30-40m range, and I’d like to be able to stay long enough – safely – to have a proper nose around. I had considered PADI’s Tec40 → Tec45 → Tmx45 route, as I am deeply into the PADI system already, but I couldn’t find anywhere to teach it straight through, and besides there are a couple of major shortcomings to that path: it limits you to 20% He, and you have to do the “deep air” Tec50 to progress, after which you can do Tmx50 but there’s no point, as you could then go onto Trimix 65 anyway. The latter looks like a good course, but I specifically wanted to avoid deep air in cold, low-vis UK waters. Another option was TDI’s Advanced Nitrox + Helitrox but that again comes with the 20% He limit. IANTD express their limits not in terms of percentages but in terms of equivalent narcotic depth, which to me indicates that they get the point of Trimix at this level of training. Finally there was BSAC’s Sports Mixed Gas. That was a total non-starter. My last experience of BSAC training meant that it would take a long, and completely unpredictable, amount of time to make happen, including the prereqs such as the buoyancy workshop. Months between a theory session and the associated practical seems the norm for them. In PADI you pay your money, in BSAC you pay your dues (and your money). And to be brutally honest, you would not want to learn real deco from people who think the BSAC88 tables† are safe!

On Day 1 I drove to Vobster from home in Hertfordshire, setting off at about 6am and arriving at about 8:30am where I met our instructor for the week Tim Clements. The first thing I did was buy a twinset, which was promptly filled for me with EANx32, all gas included in the price of the course. Not having any prior experience with manifolds, I didn’t notice at the time how stiff the valves were. Then it was upstairs to meet the rest of the team. There were a total of 6 of us, two re-sitting the written exam, one who was feeling ill so only doing the theory, 2 other “full” students such as myself, instructor Tim and instructor intern Jay of Diving Matrix. The first morning was taken up with gas planning, including accelerated deco and on backgas in case of lost deco gas. That afternoon we got in the water and practiced stage handling, such as dropping and picking up whilst on the move. That was actually the longest dive I had ever done at 1¼ hours, tho’ we spent most of it on the 6m platform. It was then that the stiffness of the valves became apparent – while I could reach them, I simply couldn’t turn them underwater and in gloves. That was incredibly frustrating and at the end of the dive I wondered if I would be able to continue with the course. Martin to the rescue, cleaning the old Crystolube out and replacing it with Tribolube. The difference was like night and day, after that the shutdown drill was a joy to do! We also practiced OOA drills, including no-mask no-reg swims.

Day 2 was all diving, more shutdown drills, more OOA practice, more stage handling including exchanging stages with a buddy while neutrally buoyant. Fun! Like air-to-air refueling for divers 🙂 Then we practiced team communication, DSMB deployment and team ascents. After this dive we got out for a debrief, then Dive 3 was exactly the same but this time with more finesse. It was this dive that decided if our in-water skills were up to diving real Trimix at NDAC. Tim is using video feedback like John Kendall of GUE, which is a powerful tool for training. Saturday was all theory, OTUs, the CNS clock, physiology and deco theory, diving at altitude, philosophy and psychology of technical diving, more gas planning, repetitive diving with the IANTD tables, END and best mix and more besides!

On Sunday we were up in Chepstow for the deep dives. Dive 4 was 20 mins @ 40 metres on 28/25 with deco on EANx50, which was amazing. Clear as a bell at that depth, no fuzziness or looming apprehension from narcosis, noticeably less work-of-breathing (WOB). The scenery left a little to be desired being just a rock face (tho’ beautifully illuminated by my Light Monkey) but still I thought it was an excellent dive. Dive 5 was planned for 15 mins @ 30 metres, by this time I was down to about 100 bar in my twinset, so I led this dive, turning it when I hit 70 and it worked out that we returned to the bottom of the shot almost bang on 15 minutes, then another accelerated deco. I had done the exam the night before at the hotel, so I handed that in, and was rewarded with Jay holding up a slate at the first stop saying “Welcome to the Darkside” 🙂 That was a total runtime of 307 minutes over 3 days of diving. Not bad!

I learnt an awful lot in these 4 days, it is an intensive course, but very rewarding, and I am eager to put these new skills into practice and really bed them in. I thought before I begun that afterwards I would be chomping at the bit to do Normoxic, but actually ART has given me a lot of new capabilities, plenty for getting on with. I wholeheartedly recommend it for anyone looking to take their first steps into Tech, and Tim as an instructor. This qualifies me to a maximum depth of 48m‡ (for which best mix for END max 24m would be 24/30, tho’ I would probably go for the GUE standard gas 21/35) and 15 minutes of accelerated deco on EANx50 or higher. There is a lot in the UK in that range.

† A table has to assume that you do your entire bottom time at your max depth, whereas a computer can give you credit for time spent shallower, which means it can give you a longer no-stop time and a shorter deco. That is one of the main reasons computers became popular. But the BSAC88s give you less deco than the computer, and unlike algos like Bühlmann and VPM that are published, BSAC refuse to divulge the research, if any, behind theirs. That might have been OK in the 80s when you weren’t considered bent unless you were convulsing and foaming at the mouth on the dive deck, but the world has moved on since then, the 88s should be abolished.

‡ If it was just depth I was after, I could have crossed over my DM to BSAC Dive Leader and gone to 50m on a single on air…