Help… I was blacking out (fainting) underwater?
This is my last resort to attempt to figure out what might have happened to me over the summer of 2007. I’m a 32 yr. old male (5’8" 200 lbs.). Every summer my wife and I travel to Sicily and spend 65-70 days there and we average 15 dives during this time. Here’s what happened and maybe someone can tell me what happened to me. Previous night of the dive: Stayed out until 3:00 a.m. (no alcohol consumption). We had been reaching the final days of our vacation and were staying out til late (the night before this one we went to bed after 1 a.m.). The day of the dive: We got up at 6:00 a.m. & drove 1 1/2 hrs. to catch a boat to take us to our dive location (we did two dives). The first dive took us to approx. 27.4 meters (roughly 90ft.) and lasted 38 minutes. We surfaced, I kept the 5mm wetsuit on & jumped into the water on 2 occassions to cool down. After 1 hr. & 10 minutes we went for our second dive that would have taken us to the lower depth of 18 meters. Here’s what happened… We were briefed by our guide and were told that we’d go down right underneath the boat (6 meters) to adjust our gear and then we’d continue our dive to the maximum depth of 18 meters. As soon as I hit the water (backwards dive into the water), I felt a tightening pressure on the left back side of my neck, as I reached the 6 meter depth I felt disoriented and a strange sensation of awareness (or lack thereof), we continued our dive and I felt sleepy and like I wanted someone to just pull me along. At approximately 13 meters, I shook my wife’s tank and signaled for her to get the guide’s attention. When he turned around he signaled to me to see if I was OK and I signaled that I was not and that I was getting out. As I was surfacing I began having episodes of blacking out (I was closing my eyes and dozing off; fighting against it, and lapsing in and out of this mode). Once we surfaced I felt exhausted and continued this way for a few days (laxed). This happened in late August 2007 and I still feel neurological effects similar to what happened that day (I feel lightheaded or dizzy often). Can someone help? Please, I need to know what might have happened. Thank you.

Sounds Like shallow water blackout (Latent hypoxia)

I have seen several cases and have suspected regulator failure or malfunction.

wiki did surprise me on this one

The last paragraph is his very good

good luck, former EMTP WSIT