I had my first scare on a night boat dive recently, and want to share the story for my own sake, but also in case there is anything for others to learn. Sorry for the long wall of text...
Lead up
We were a group from the local dive club heading out on a usual evening boat dive, diving in teams of 2-3 with a dive leader/boat operator staying in the boat to pick us up when surfacing. It's cold water diving in the dark, with not too great viz - all pretty standard around here. We had to switch the buddy teams around a little bit to accommodate a new diver in the group, so I was paired with a CC diver I haven't dived with before - I was diving OC doubles with EAN32. We agreed on a plan of max 100ft, and he showed me how he donates on his rig before we splashed. I let him lead the dive as he was more experienced and knew the dive site better. We were briefed by the dive leader on which direction to swim because of the conditions and where it would be easier for him to pick us up. We descended quickly to about 100ft and started swimming along a wall as we planned. The wall goes down to 300ft+, but that's not something that has ever bothered me. I noticed a little buzz from narcosis as I often do at this depth. Usually it slows my breathing down and relaxes me, but after around 60 dives, I'm still a little wary of the feeling and it can also make me a little nervous/hyper-focused. We were swimming pretty calmly, frog kicking along, I was checking my computer, my SPG, paying attention to the bottom time, NDL, and staying close to my buddy.
The incident
At around 18-20 minutes into the dive, right after signalling to my buddy that we should ascend to a shallower depth to stay well within NDL, I suddenly started feeling dizzy. It was not like vertigo/spinning, but a feeling that my mind wasn't keeping up with my senses, I was sluggish. Usually it feels like everything slows down when I get slightly narced, but this was a much stronger version of that, and it felt like my vision was just seeing a sequence of still frames rather than a smooth video - as if the framerate was too low. At the same time I felt anxiety rising, and I immediately signaled my buddy that I wasn't feeling well and I thumbed the dive. I remember being scared, worst case scenarios started running through my mind, especially being afraid that it would get worse and that I didn't know what caused it. But I knew that ascending to a shallower depth hopefully would ease the symptoms. We turned around and started ascending when it really hit me. It was all kind of a blur. But I remember 3 things happening at once: A feeling of panic, my mask flooding, and hyperventilation. I felt like I couldn't breathe and I remember thinking "Oh sh*t. This is bad. I don't want to die. Don't panic. Hyperventilation is bad. CO2 makes you feel like you can't breathe. Remember to exhale. Control your breathing! Relax! Ascend, but not too quickly." At least my training kicked in, and I knew instantly that I did not want to bolt. If anything I was afraid of ascending too quickly, so I knew I had to deal with it underwater.
I managed to exhale, slow my breathing, clear my mask and regain control. I'm not sure how long this took. It felt like a long time, but the worst of it was probably only 20-30 seconds. My mind still felt a little muddy, and I was shook by the whole incident, as we continued the ascent while swimming back along the wall in the direction we had come. Now I could feel we were heading into a pretty strong current. I was aware of my buddy being close to me, but I also felt a very strong narrowing of focus and a general lack of awareness. I'm not sure I would have been able to help my buddy if he had a problem at that moment. We stabilized at around 50ft. My mind was clearing a little bit, and my buddy asked me if I was OK. I signaled back OK because I was feeling better – but I'm not sure if that was the right thing to do, I was still not feeling great. He pointed out a big crab, maybe to distract me, or maybe because he didn't realize how bad my experience had been. I was still very nervous after what happened, so I gave my buddy the thumb again to make sure he understood that I still wanted to end the dive, and we ascended. On the way up, I experienced the strongest current I've ever been in, with the added complication of very low viz from a halocline of brackish water and lines from lobster traps all around us. I remembered thinking I shouldn't be kicking too hard against the current to avoid exhaustion, but I was also a bit sceptical of just letting myself drift and possibly lose sight of my buddy in these conditions. I held on to the rock face of the wall for a bit, and on the way up we also hung on the line for a little bit, careful not to get entangled, and soon we were on the surface getting picked up by the boat. While surfacing I felt a pretty strong headache coming on, and I felt winded and a bit nauseous getting back on the boat. On the boat I could see we drifted fast, by my estimation somewhere close to 4 knots. While sitting on the boat, trying to breathe deeply I noticed the weight belt was a little tight, so I unbuckled it. Wow, it was tighter than I had thought, suddenly I could feel how restricted my breathing had been, when I could finally breathe deeply into the belly. My buddy seemed a little surprised at the surface that it felt so severe to me, and he said I seemed very calm under water. I guess that's a good thing, but it also highlights some possible issues with my communication. Gradually my headache dissipated, and the other guys on the boat shared stories about similar incidents they had experienced. It was definitely a scary experience, but I am determined to learn from it and improve as a diver.
My theory:
In hindsight, the first thing I noticed, in the moments leading up to the dizzy spell, was a slight feeling of being uncomfortable. I remember working a little bit more than usual with my buoyancy, feeling a little unstable. Specifically I felt like whenever I didn't pay attention I was descending a little, and I didn't want to exceed my max depth of 100ft. I often feel a little bit more slow/deliberate when I'm at this depth, but I remember making several small adjustments and that I was paying close attention to my depth gauge, already a narrowing of awareness and possibly a slight paranoia. My theory is that I had already been breathing a little bit more shallow than usual, maybe partly because of a tight weight belt and being a little uncomfortable. This might have contributed to an elevation of CO2 levels, that again made my narcosis worse. The narcosis, as well as a shallower breathing pattern, might have affected my ability to deal with my buoyancy effectively enough, which again could have made me breathe more on top of my lungs. Many small mistakes adding up over time. After getting dizzy and thumbing the dive, I suspect turning into the current might have been enough to push me over the top and start the hyperventilation and the rush of anxiety. I don't know how my mask flooded, or the exact sequence, as my memory of it is blurred, but I know that my mask strap was quite loose and it is possible that either the current or my very snug hood pushed the skirt enough to flood it. I regularly practice taking my mask off underwater, so I don't think the mask flooding was the cause of my hyperventilation, but it probably made it worse.
My takeaways:
* As you might be able to tell from this wall of text, I'm a very meticulous, deliberate and careful guy. I always respect the limits of my training, and try my best to do everything right and stick to correct procedures. The flip side of that is that I have a tendency of over-thinking. Sometimes being overly careful can take up too much of my awareness, and I have been trying recently to just relax and push my comfort zone a bit. Maybe I overcompensated, and should have recognized the early discomfort and acted sooner...
My questions to you:
Lead up
We were a group from the local dive club heading out on a usual evening boat dive, diving in teams of 2-3 with a dive leader/boat operator staying in the boat to pick us up when surfacing. It's cold water diving in the dark, with not too great viz - all pretty standard around here. We had to switch the buddy teams around a little bit to accommodate a new diver in the group, so I was paired with a CC diver I haven't dived with before - I was diving OC doubles with EAN32. We agreed on a plan of max 100ft, and he showed me how he donates on his rig before we splashed. I let him lead the dive as he was more experienced and knew the dive site better. We were briefed by the dive leader on which direction to swim because of the conditions and where it would be easier for him to pick us up. We descended quickly to about 100ft and started swimming along a wall as we planned. The wall goes down to 300ft+, but that's not something that has ever bothered me. I noticed a little buzz from narcosis as I often do at this depth. Usually it slows my breathing down and relaxes me, but after around 60 dives, I'm still a little wary of the feeling and it can also make me a little nervous/hyper-focused. We were swimming pretty calmly, frog kicking along, I was checking my computer, my SPG, paying attention to the bottom time, NDL, and staying close to my buddy.
The incident
At around 18-20 minutes into the dive, right after signalling to my buddy that we should ascend to a shallower depth to stay well within NDL, I suddenly started feeling dizzy. It was not like vertigo/spinning, but a feeling that my mind wasn't keeping up with my senses, I was sluggish. Usually it feels like everything slows down when I get slightly narced, but this was a much stronger version of that, and it felt like my vision was just seeing a sequence of still frames rather than a smooth video - as if the framerate was too low. At the same time I felt anxiety rising, and I immediately signaled my buddy that I wasn't feeling well and I thumbed the dive. I remember being scared, worst case scenarios started running through my mind, especially being afraid that it would get worse and that I didn't know what caused it. But I knew that ascending to a shallower depth hopefully would ease the symptoms. We turned around and started ascending when it really hit me. It was all kind of a blur. But I remember 3 things happening at once: A feeling of panic, my mask flooding, and hyperventilation. I felt like I couldn't breathe and I remember thinking "Oh sh*t. This is bad. I don't want to die. Don't panic. Hyperventilation is bad. CO2 makes you feel like you can't breathe. Remember to exhale. Control your breathing! Relax! Ascend, but not too quickly." At least my training kicked in, and I knew instantly that I did not want to bolt. If anything I was afraid of ascending too quickly, so I knew I had to deal with it underwater.
I managed to exhale, slow my breathing, clear my mask and regain control. I'm not sure how long this took. It felt like a long time, but the worst of it was probably only 20-30 seconds. My mind still felt a little muddy, and I was shook by the whole incident, as we continued the ascent while swimming back along the wall in the direction we had come. Now I could feel we were heading into a pretty strong current. I was aware of my buddy being close to me, but I also felt a very strong narrowing of focus and a general lack of awareness. I'm not sure I would have been able to help my buddy if he had a problem at that moment. We stabilized at around 50ft. My mind was clearing a little bit, and my buddy asked me if I was OK. I signaled back OK because I was feeling better – but I'm not sure if that was the right thing to do, I was still not feeling great. He pointed out a big crab, maybe to distract me, or maybe because he didn't realize how bad my experience had been. I was still very nervous after what happened, so I gave my buddy the thumb again to make sure he understood that I still wanted to end the dive, and we ascended. On the way up, I experienced the strongest current I've ever been in, with the added complication of very low viz from a halocline of brackish water and lines from lobster traps all around us. I remembered thinking I shouldn't be kicking too hard against the current to avoid exhaustion, but I was also a bit sceptical of just letting myself drift and possibly lose sight of my buddy in these conditions. I held on to the rock face of the wall for a bit, and on the way up we also hung on the line for a little bit, careful not to get entangled, and soon we were on the surface getting picked up by the boat. While surfacing I felt a pretty strong headache coming on, and I felt winded and a bit nauseous getting back on the boat. On the boat I could see we drifted fast, by my estimation somewhere close to 4 knots. While sitting on the boat, trying to breathe deeply I noticed the weight belt was a little tight, so I unbuckled it. Wow, it was tighter than I had thought, suddenly I could feel how restricted my breathing had been, when I could finally breathe deeply into the belly. My buddy seemed a little surprised at the surface that it felt so severe to me, and he said I seemed very calm under water. I guess that's a good thing, but it also highlights some possible issues with my communication. Gradually my headache dissipated, and the other guys on the boat shared stories about similar incidents they had experienced. It was definitely a scary experience, but I am determined to learn from it and improve as a diver.
My theory:
In hindsight, the first thing I noticed, in the moments leading up to the dizzy spell, was a slight feeling of being uncomfortable. I remember working a little bit more than usual with my buoyancy, feeling a little unstable. Specifically I felt like whenever I didn't pay attention I was descending a little, and I didn't want to exceed my max depth of 100ft. I often feel a little bit more slow/deliberate when I'm at this depth, but I remember making several small adjustments and that I was paying close attention to my depth gauge, already a narrowing of awareness and possibly a slight paranoia. My theory is that I had already been breathing a little bit more shallow than usual, maybe partly because of a tight weight belt and being a little uncomfortable. This might have contributed to an elevation of CO2 levels, that again made my narcosis worse. The narcosis, as well as a shallower breathing pattern, might have affected my ability to deal with my buoyancy effectively enough, which again could have made me breathe more on top of my lungs. Many small mistakes adding up over time. After getting dizzy and thumbing the dive, I suspect turning into the current might have been enough to push me over the top and start the hyperventilation and the rush of anxiety. I don't know how my mask flooded, or the exact sequence, as my memory of it is blurred, but I know that my mask strap was quite loose and it is possible that either the current or my very snug hood pushed the skirt enough to flood it. I regularly practice taking my mask off underwater, so I don't think the mask flooding was the cause of my hyperventilation, but it probably made it worse.
My takeaways:
- It happened so fast. Mistakes add up underwater, and it escalates QUICKLY
- STOP BREATHE THINK ACT - I should have stopped moving and concentrated more on my breath the second I felt dizzy.
- Be careful not to tighten the weight belt too much
- Always make sure you can and do breathe slowly, comfortably and deeply
- I'm very glad I always have a buddy, just knowing we were two divers to solve the issue was reassuring
- Don't fight the current. Especially in a situation like this. I should have relaxed more and we could have done a more efficient drifting ascent together.
- I'm happy I managed to control my breathing and make a safe ascent.
- I should probably communicate more clearly that I'm not feeling well
- Maybe look for signs of being uncomfortable earlier, and ascend to a shallower depth if I'm not comfortable*
* As you might be able to tell from this wall of text, I'm a very meticulous, deliberate and careful guy. I always respect the limits of my training, and try my best to do everything right and stick to correct procedures. The flip side of that is that I have a tendency of over-thinking. Sometimes being overly careful can take up too much of my awareness, and I have been trying recently to just relax and push my comfort zone a bit. Maybe I overcompensated, and should have recognized the early discomfort and acted sooner...
My questions to you:
- Do you agree in my assessment that it was a CO2 buildup/hit?
- I wasn't overexerting myself when it started, and I'm in pretty good shape, but my breathing had been restricted.
- The headache also seems to support this...
- Any comments on what happened, the way it was dealt with, my thoughts about it?
- Have you experienced something similar on OC? Was it caused by CO2 or do you suspect something else?
