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What I'm about to describe is a dive I carried out a little while ago and I 
would like any constructive opinions as to what might have been the problem. I 
made a couple of blatant mistakes, these I will point out. Please donjt waste 
everybody's "on-line" time proliferating emails discussing these mistakes, 
just the cause of what I experienced.

The dive was to 45m for 20 mins then 35m for 30 mins. Deco schedule was 12m 
for 4mins, 9m for 6 mins, 6m for 10 mins and 3m for 18mins. 

Bottom gas was air, deco gas from 9m upwards was EAN80.

The bottom time element of this dive went well, the first problem arose when I 
came to deploying my delayed SMB (Surface Marker Buoy - not to be confused 
with SMD).

Due to a mixture of fatigue and narcosis, I connected my reel to the SMB by 
its lanyard rather than the end of the line, proceeded to inflate it and 
wondered why despite pulling the clutch to let the line out I was starting to 
go up as well. OK no problem, I instinctively let go, bye bye SMB. I'm now 
sitting on top of the wreck half cursing myself and half laughing as this is 
not the end of the day I'll make an ascent with out SMB. Then I spotted one of 
the other divers off the boat about to deploy his SMB. So I go over to him and 
signal that mine has gone and I come up with him using him as a visual 
reference. Keeping our distances to avoid a cluster fuck.

The ascent to 12m was OK, though I found it quite an effort to remain upright 
in the "seated" position like one would normally, if slightly negatively 
buoyant and hanging on a SMB, due to the deco tank on my front. If I relaxed I 
found myself face down, feet going up slightly all this making it harder to 
maintain depth precision unless I started finning a little. Then comes the 
ascent to 9m and the switch to EAN80. At first this is OK, however I realise I 
am not maintaining 9m all the time sometimes dipping down to 11m. By this time 
I'm getting tired and am in a face down position due to the cylinder pulling 
down.

Then it happens, the most weird feeling in the back of my head rising up as 
though to engulf my mind in a kind of dizziness. I switch back to my air and 
get the attention of the other diver nearby and I hold onto him whilst it 
passes. I signal to him that something isn't right with my deco mix, which is 
the only thing I can think of. By this time we have ascended to the 6 m stop. 
So now I switch back to EAN80 and carry out my stop as planned and the 3m stop 
with an extra 15mins added in case the air break has penalised my deco 
schedule.

Upon reaching the surface all is OK etc and home we go.

OK, the (main) mistakes are that obviously I assembled my SMB wrong. Normally 
it is already assembled ie SMB clipped to reel line and is dedicated to the 
purpose. Secondly I didnt have a spare SMB, normally I would have my lift bag 
for bringing portholes etc to the surface and my other reel which I use for 
wreck penetration. If I had this I could have deployed it and my ascent would 
have been less tiring/stressful.

What I would like an opinion on is given the dive profile and the added 
fatigue I experienced do you think I was on the verge of getting an O2 hit ?

If not then what the hell could it have been ?

regards
Lawrence
 

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