Preparing for Devil's Throat

[TSandM]

130 feet is roughly 5ATA, which means a 1.4 ppO2 would be present if you were diving 28%. 28% is going to give you some increased NDL time compared with air.

 

[Mossman]

130 feet is roughly 5ATA, which means a 1.4 ppO2 would be present if you were diving 28%. 28% is going to give you some increased NDL time compared with air.

1) Do the Cozumel air fill establishments pump 28%? I thought it was the standard 32 or 36.
2) What dive op would want to take nitrox divers to Devil's Throat knowing they would diving right at their MODs. After all, it's one thing to handle a rogue diver going into deco, yet another to handle a diver ox-toxing.

 

[scubafanatic]

1) Do the Cozumel air fill establishments pump 28%? I thought it was the standard 32 or 36.
2) What dive op would want to take nitrox divers to Devil's Throat knowing they would diving right at their MODs. After all, it's one thing to handle a rogue diver going into deco, yet another to handle a diver ox-toxing.

1) you're right, 32% (and less commonly 36% EAN) ARE the standard mixes, mass produced by the one or two giant tank filling 'factories' on the island the vast majority of Cozumel dive ops use. There are a few dive ops with in-house fill operations/compressors that could do custom mixes like 28 % EAN.

2) The large numbers of divers doing Devil's Throat (and other deep sites) without ox-tox issues are ample evidence that the ppO2 'limits' of 1.40 are excessively conservative.

 

[ggunn]

2) The large numbers of divers doing Devil's Throat (and other deep sites) without ox-tox issues are ample evidence that the ppO2 'limits' of 1.40 are excessively conservative.

Conservative, yes, but excessively so? Is the lack of airliner crashes ample evidence that aircraft safety measures are excessively conservative? How many O2 toxicity incidents would it take to indicate that the ppO2 limits were set correctly?

 

[Dave Dillehay]

When we do the entire south part of the Punta Sur Reef with 28 or 32 % nirtox (with a nitrox cetified group of 6), we have a grand finally down the Devil's Throat and exit the shallow part at 117ft. That is the most kick ass dive in the Caribbean. BTW, the time at max depth is usually only a minute at most.

On the other hand, diving with air directly into the Devil's Throat, it is very comforting to come out on that deep blue wall with 2700 PSI and still have plenty of time to enjoy all the other neat swimthroughs as we work our way up. That dive usually lasts 45-50 minutes.

AS BolderJohn infers, ANY dive site in Cozumel can be the worst--or the best.

Dave Dillehay
Aldora Divers

 

[Ron Lee]

2) The large numbers of divers doing Devil's Throat (and other deep sites) without ox-tox issues are ample evidence that the ppO2 'limits' of 1.40 are excessively conservative.

My GUESS is that almost all of the folks doing Devil's Throat are doing it on air so the ppO2 at around 130' would be 5 x 0.21 or 1.05 so not that close to the ppO2 value of 1.4.

 

[Dave Dillehay]

Again, it is not necessary to go to 130 ft, when there is a nice exit at 117ft, and also again, you should be there for less than a minute. Let's remember that oxygen toxicity is time dependent as well.

Dave Dillehay
Aldora Divers

 

[halocline]

Dave, that's a nice description of your dive, but do you have any control over who else might be on the site while you're there?

 

[Dave Dillehay]

Dear Halocline

It is simple, if there is another group there we just enjoy the myriad of other neat holes until our rise to the top of the reef. Occasionally we double back on the shallow sandy side (close to the reef staying out of the current), then rise to the top of the reef drifting north and watch all the bubbles coming up. Again, normally we ascend to our safety stop at the end of the reef. But with plenty of air/nitrox we have many ways to make that place less boring than some have described.

Dave Dillehay
Aldora Diver

 

[1erCRU]

Last year a number of us were joking that the name "Devils Throat", should be changed to something less ominous like: "Tunnel of Love". Since it's actually a pretty benign dive, virtually no current, lots of light infiltration and numerous exits from the general structure. Would there even be a tread on the subject with a name change like that? Steel 120s, Nitrox, & Computers, do much to assuage the NDL/time/depth related concerns.

After nearly 30 years of diving it, I can easily recall my 1st time (on air, Al80, jet fins, NO computer, etc). I was feeling a bit apprehensive during the briefing and early on the decent, but that was all wiped away by the incredible vis, warm temp, and beautiful reef structures. Admittedly, inside, I followed the guys in front of me VERY closely, but I was generally fascinated and looking around with my light for critters. The only moment of pause was the turn into the throat, I was not looking at the guy in front of me but off to the side, and turned to just catch a glimpse of his now, disappeared fins, leaving me alone. Someone a long time ago (over dramatically) called that turn a "Leap of Faith", I made the turn, went down the throat and had a totally unexpected thrill as I looked down and ahead to the incredible contrast between the darkness of throat and the brilliant BIG BLUE exit. That still lights my fire even after 25-30 dives into "throat".

It's not my favorite dive (only the NEXT dive is) but it has it's own beauty. I have even made a night dive on it, but it was not nearly as interesting as I thought it would be.....now Punta Sur Sur......?