An interesting dive day

[MaxBottomtime]

Merry Passage and I had an interesting day yesterday. We had excellent visibility at Biodome, a small reef off Pt. Vicente. Hermissenda opalescens covered the reef by the thousands. We struck out for the fourth time in our search for Babakina festiva, but still had fun. We made a second dive at Torrance Reef to look for Doto columbiana, which are numerous there. I found three Cuthona divae together, which I have never seen before.

I've had an airfill card sitting unused for a few years, as I've been diving primarily nitrox. Earlier this month, I filled my tanks with air just to finish off the card. Yesterday's dives were 70 feet for 72 minutes followed by a 1:13 surface interval, then a second dive to 60' for 1:03. I followed my computer, ascending with a few minutes of ndl on each dive. It wasn't until I was rinsing my gear that I realized my computer had reset to 32%. I'm sure I skipped quite a bit of deco obligation. In 43 years of diving, I have never made a mistake like that. I didn't get bent, but I will certainly double-check my computer before getting in the water again.

Apostichopus californicus, Warty sea cucumber
This resembles my pucker factor when I realized I had skipped deco stops.

I felt better when I hadn't been bent by the next day.

More photos at Interesting dive day

 

[DavidFL]

Glad it didn't end badly. I'm an electrical engineer (although that curriculum was a very long time ago before integrated circuits!) and both of my computers are Shearwaters, but I still get surprised from time to time at a setting that somehow is not what I thought I had "left" it at!

 

[scubadada]

Hi @MaxBottomtime

I'm very glad you are OK, you skipped reasonably significant deco. I just couldn't stand it, ran your profiles on MultiDeco. I ran them at a GF high of 95. Probably a bit over estimate as your computer showed no deco on 32%. Nevertheless, you did not do the deco on your 1st dive before the 2nd. I have dived a computer on air when actually diving nitrox, but never the other way around. What a story! Teaches us all a good lesson, thanks.

Here are the 2 dives on air and then on 32%:

 

[MaxBottomtime]

My average depth on dive #1 was 56 feet, but yes, I got lucky.

 

[johndiver999]

what kind of ascent did you do? If you came up slow, did a 4-5 minute "safety stop", that may well have made the difference.


Also, since you always dive 32% (it sounds like) weren't you at least expecting a markedly shorter ndl on the second dive? Perhaps the first dive when the computer being on air, was shortening your displayed ndl (for the second dive) enough to fool you?

 

[MaxBottomtime]

I should have, but I was concentrating on my search for a certain nudibranch. I look at my spg often, but not my computer. I also discovered that the computer didn't have a glitch, I did. I made a dive two weeks ago using one of Merry's tanks. I set the computer to 32%, then forgot to set it back to 21% when I used my tanks. In 2700 dives, I've never done anything like that. If it ever happens again, it's time to get myself checked out.

I always do an annoyingly slow ascent, then look through my photos from the dive during the safety stop. I made a seven minute stop on the first dive, then a ten minute stop on the second.

 

[RVBldr]

And assuming the total run time was 72 min, not actual bottom time?

 

[MaxBottomtime]

I checked the anchor at 70 feet in the sand, then spent the next 61 minutes around 55 feet followed by a ten minute ascent, so I was within my ndl. The second dive is where I got lucky. After a 1:13 surface interval, I spent 50 minutes at 60 feet before a 13 minute ascent. Fortunately, I like to look through my photos during the safety stop, so I spent nine minutes at fifteen feet.

 

[johndiver999]

A 13 minute ascent is a lot of deco. Even if it is not all at 10 ft. Maybe that is one of the lessons. I’ve screwed up too with mix, not too many months ago found myself diving at 135 with 36% and was wondering why I seemed to be having some blurry vision, didn’t know I screwed up until I got on the boat and found I still had the same 2 bottles left of 32 that I started with. A significantly worse error.

 

[scubadada]

Hi @MaxBottomtime

Looks to me like you may have skipped very short deco obligations at the worst. Perhaps saved by reviewing your photos at the long "safety" stops. Again, run at a GF high of 95, stop time 1 min.