Narked by Cold?

My buddy, finding Thunderbird Four 

Well my last dive was ...interesting. In the sense that the final part of it involved me learning first-hand that my ability to safely do a free ascent from a depth greater than 10m in my drysuit is something that needs work. Also, that I will never again forget to clip my SMB (Surface Marker Buoy) to my jacket - lesson learned. It would have been very helpful to have the cord as a visual reference point when trying to ascend. On the other hand, I was having enough to deal with the incessant "YOU ARE GOING UP TOO FAST STOP THAT NOW OR YOU WILL DAMAGE YOUR LUNGS YOU FLAMING IDIOT" beeps from the computer, the fact that I couldn't seem to balance the weight in my jacket and the air in my suit to be neither sinking nor rising, and the fact that my mask chose this moment to fill with water.

I distinctly remember having a second or so's brain space to think "Hmm. This isn't working out how I planned" in the middle of the "Well, shit, what now?" situation.

I solved the problem by dropping down a bit, stabilising, then ascending and swimming across to a nearby rock ledge at 6m, when I floated around doing a safety stop, clearing my mask and thinking baleful thoughts at my computer. And at my own stupidity. Luckily my buddy was fine, although he had his hands full shepherding some very new divers back to the exit point.

The second dive went much better, as myself and my buddy retraced our steps, and I practised a safe ascent, which went better. The only odd thing about that dive was that towards the end, my buddy signalled "I am cold, let's turn around" (he wears a wetsuit). We immediately turned round, but he suddenly paused, and picked up an object (I think a discarded metal ring from someone's dive kit) from the quarry floor. He then swam around for a while, looking for something, then carefully placed the object on the rock and swam off.

This is unusual behaviour, as most divers who have signalled "Cold" will start kicking with some speed once the end of the dive (and a nice cup of tea) is in site. I asked him about it later, and he commented "It just seemed really important to do that". We both pondered this, as this sort of fixation with completing a specific task, without thinking about the dive plan, is characteristic of nitrogen narcosis. However, we were only about 8m deep at the time, which is way too shallow for narcosis to kick in.

Was it exertion and cold causing a slight form of narcosis, or was it slight hypothermia? No way of knowing, but an issue to be aware of; that would be more of a problem if we were in the North Sea needing to get back to the ascent point, and then climb back into a boat.

Other than that, though, it was an interesting dive. And we found Thunderbird Four.