Here's the set-up. It is relevant, I promise
As some of you know, I am one of the authors of the Tahoe Benchmark. This is a semi-annual test of scooters. We test scooters over the lengths of a surveyed 1/4 mile underwater track.
The track is exactly 36' deep on the side of a slope; there are markers every 100' that mark the length of the track. It's easy to run the track, just look at the depth gauge every once in a while and stay at 36', and follow the markers. Easy peasy.
I would estimate I have well over 100 miles underwater along this track testing scooters. I know it like the back of my hand (probabally better, actually).
Well enough, that I can easily run the track without refering to a depth gauge.
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So, here's what happened:
We'd received a scooter from SS to test. It needed to be tested in tech gear, so I loaded up a set of doubles that were about 1/3 full of 21/35, I figured I may as well use it up.
When I arrived at the track, I realized I'd forgotten my computer. <shrugs> it's no big deal, 36 feet deep and 16 minutes max. So, in I went.
As I ran the track, I left one of the markers behind. The next one didn't show up when I expected it; then I realized with a shock, I'd just gone by a log that sits at about 60' deep! Wow. I angled uphill, and reaqquired the track. This happened twice more.
Afterwards, I realized that using nitrox gives me a subtle narc at track depth that I had learned to use in keeping depth. Using 21/35, this depth reference was gone.
The next day I ran the track twice, once using nitrox 32, and the other, air. Both times I was able to accurately run the track at a steady 36' without a depth gauge.
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Here's what I learned from the weekend:
- Depths as shallow as 36' do produce a narc that affects you.
- Air and nitrox produce similar narcosis.
All the best, James