DCS after a deep, wreck, night dive

REPORTED STORY

I am qualified advanced open water diver. I am reporting an accident that occurred during a recent dive to 45 meters (148 feet) depth. At the time of the dive, I had 230 logged dives, over three and a half years. I have had two previous dives to 41 meters (135 feet).

I was tagging onto a dive with two other divers who already had a dive plan made a week in advance. The 45 meters dive was to be the only dive of the night. I had dived with Buddy One a few times. This was the first dive with Buddy Two. I had dived the site many times, and to 41 meters at the same spot, but in daylight. Visibility is generally good at this site; 8-15 meters visibility is normal. This dive was around 8 meters (26 feet) visibility. Water temperature was 6?F. As this was my deepest dive to date, I planned my gas carefully. I planned to have 15 liters steel tank on my back, with an 11 liters tank at 200 bar at the stage. Both buddies had twin 12's.
I had only used the 11L stage configuration once before. Normally I dive a 15L with 3L pony. Occasionally a 7L stage (only twice so far).

I planned my gas, consumption, cylinder switches. All was on a wrist slate so that I could see if I started to fall short during the dive.

I figured as this was my first night dive at the site, and my deepest dive to date, I should not take my camera rig that I normally take on every dive. However, on dive day, the temptation of wrecks in the dark in good vis was too much, so I took the camera rig.

Pre-dive planning was in the café at the dive site. It was agreed that the other two divers would go to a small cruiser boat wreck at 47 meters (154 feet). If I was not comfortable, I would hang above at 43-45 meters.

Total dive time was to be 1 hour 8 mins.

After around one min at 47 meters depth, we would swim and ascend to the next wreck, a helicopter at 24 meters (79 feet), along various wrecks on the 20 meters (66 feet) shelf, then finally shallowing up to make the safety stop, and around 10 mins deco by the quarry wall. This would be my first deco dive.

The dive started well, with a short three minutes swim at 15 meters (49 feet), then over the edge, descending to 47 meters; reaching 47 meters at 6 minutes. I went all the way to 47 meters and placed my hand on the top of the cruiser boat. I took a few photos. I suddenly felt a numbness, and tingling in my lips, then tunnel vision closing in.

I never had narcosis on a dive but recognized it immediately. I knew this could be a very dangerous situation and needed to act fast.

I had an urge to reduce depth quickly to make the narcosis go. However, I went up too quickly. I went past a deep stop of 23.5m (77 feet). I arrested the accent at 23 meters (75 feet). I ditched my air as fast as I could to prevent a runaway accent, and so became negative, and dropped down again to 35 meters (114 feet). At this point, I was still narked, with elevated heart rate. Also, I was aware I was using air quite fast, and didn't want to accidently get into a fast accent. For security backup (assent and air), I grabbed and held onto Buddy One's BCD (I had spotted Buddy One when I descended back down) so we could ascend together. At this point, my torch went flat despite being charged fully the night before. I didn't try to get out my back up as one of my video lights on my camera rig was on, so I used this until the situation was stabilized. I was aware I needed to switch cylinders so that I still had backup in my back cylinder if I had equipment failure. Under the stress of the situation, I still managed to check my SPG, I checked the regulator was working, and then made the switch.

What I did not know was that although I was monitoring my ascent rate and position, Buddy One was compensating buoyancy for us both. When we ascended too far (past 10 meters [33 feet]), I released Buddy One so I could drop back down to a safer depth. This meant Buddy One had enough air for himself and some of my buoyancy, so he went up in an uncontrolled assent for the last 10 meters and broke the surface. This meant he went from 47 meters to surface in 4 minutes with a decompression obligation. He immediately descended back to me, and Buddy Two at 24 meters (79 feet).

All settled down, and arrived at the helicopter, wreck 2 of the original dive plan. At this point, all was calm and OK. I checked my pressure and I had 104 bar remaining in my 15L with a decompression obligation of 8 minutes. My 11L had plenty of air as I had only used it a few mins. We were now 16 minutes into the dive. I was fine and calm now, and was able to dive fine, and took photos of the other two in the wrecks. The dive continued to the airliner fuselage at 24 meters. We swam though. My deco obligation has increased to 10 minutes. I switched back to the 15L 30 minutes in as we began to ascend.


We ascended midwater in the dark with only computer as reference. We had used more air than planned, so could not make it as far as the quarry wall before we had to ascend for the deco stop. I carried out the 10 minutes mandatory stop. My computer then switched to an 8-minute optional stop. At this point, the 15L was at 30 bar. I switched to the 11L. I remained on the 11L until the end of the dive. Maintaining a depth between 3 meters (10 feet) and 6 meters (20 feet) for 17 minutes in the dark midwater was very tricky. I went up to 2.9 meters once. Often, I dropped below 6 meters. I was doing a lot of finning up and down, adding and dumping air. It was difficult to maintain the depth with floaty cylinders. At the end of the dive at 53 minutes, I surfaced with 30 bar in the 15L and 20 bar in the 11L, with all deco on my dive computer cleared.

Although the dive was out of plan for a lot of the dive, I did manage to monitor my depth, gas on two cylinders and when to switch; noticed when I was narked and needed to shallow up; and recognized and controlled fast accents. Total dive time was 53 minutes.

The dive resulted in slight joint aches noticed on the journey home. I called the dive chamber at midnight when I arrived home. They asked me to come in for treatment 8:00 a.m. the next morning as it was mild symptoms, immediate re-compression was not required. I was treated with Table 62 at 18m in the hyperbaric chamber with one extension. Also, two days later with an additional hour 40 min hyperbaric treatment at 14m. This resolved joint pain, and slight balance issues consistent with a mild CNS bend. There were no lasting symptoms. Buddy One and Buddy Two had no symptoms.

Upon reflection, there were just too many new factors in this dive. Diving past my qualification depth without training. Making my deepest dive at night. Making a challenging dive with a new gear set up (the 11L), and task loading with the camera, and unfamiliar buddies.