Bahamas Diving-Split from Spiegel Accident

[Trace Malinowski]

Just a curious question... Doesn't O2 toxicity start somewhere around 218'? Or is it deeper?

At 218 feet you are at a ppO2 of 1.6 ATA. The pressure of oxygen is only one factor that will determine the risk of oxygen toxicity. CO2 is another problem that exacerbates the likelihood of oxygen toxicity and contributes to narcosis and DCS. Breathing a dense gas such as air at depth, or performing work such as swimming at depth, may increase CO2 and increase the risk of oxygen toxicity. Using helium to make breathing easier by reducing gas density and using scooters for propulsion rather than swimming are two strategies to help reduce oxygen toxicity risk.

The greater the percentage of oxygen, the less nitrogen exists to "depress" the body's reaction to oxygen. You may be able to get away with breathing air at greater ppO2's than 100% oxygen at the same ppO2's. Divers have successfully ventured far deeper on air and have been subjected to higher ppO2's than 1.6 ATA. This is considered "extreme exposure" and has been done successfully and also tabled for emergencies and contingencies. While divers are usually cautioned not to exceed 1.4 ATA for a working portion of a dive, such as swimming, divers have experienced toxicity at 1.3 ATA and less. On air, a ppO2 of 1.4 ATA will place a diver at 187 fsw, a ppO2 of 1.3 ATA at 171 fsw, and a ppO2 of 1.2 at 155 feet. Meanwhile, using trimix, 18% oxygen and 45% helium at 218 feet will place a diver at a ppO2 of 1.37 ATA and on 15% oxygen and 55% helium the diver will be at a ppO2 of 1.14 ATA.

Deep air diving is risky enough for trained technical divers, and is far more dangerous for the untrained recreational diver who decides to venture deep on air without knowing the risks, without better training, and without a better mindset to problem recognition and resolution, including planning dives with better tools and gases.

 

[divin'dog]

So would taking divers on air down to the 225' discussed in this thread be borderline safe?... Dangerous?

Isn't this taking a risk?

 

[Dantheengineer]

Depends on where you draw the line. Is diving "Safe" at all?

 

[Dr Wu]

So would taking divers on air down to the 225' discussed in this thread be borderline safe?... Dangerous?

Isn't this taking a risk?

Aparently it is not at this resort.

 

[battles2a5]

So would taking divers on air down to the 225' discussed in this thread be borderline safe?... Dangerous?

Isn't this taking a risk?

From a textbook perspective, doing a bounce dive to 225 on air is not going to put you at significant risk of O2 toxicity. You won't be spending long enough above 1.6 to really make a difference. This is not to say that it can't happen, but it is not likely.

Narked out of your skull? Probably.

Pushing the limits of an AL80? You bet.

Leaving little to no options if the crap hits the fan? Uh-huh.

Risking an ox-tox event? Not likely, but you have other things to worry about

 

[k374]

that website states that all their dives are non-deco, I thought non-deco with AIR was 130-140' or so max? Per my computer the NDL at 140' is 5 mins so how are these guys going to 185' and still managing a no-deco dive? am I missing something....

 

[gcbryan]

that website states that all their dives are non-deco, I thought non-deco with AIR was 130-140' or so max? Per my computer the NDL at 140' is 5 mins so how are these guys going to 185' and still managing a no-deco dive? am I missing something....

I checked the website but didn't see where it said that all of the dives were non-deco.

On some of these dives I'm sure the answer is that a deco obligation is incurred but due to the multi-level nature of the dive is satisfied before you get too shallow.

However, if you should have a problem at depth and go straight up you would have a problem.

I think they get away with these dives by making a distinction between their regular dives and their "custom" dives. It doesn't sound like the best idea...you will be diving with redundant "cave diving" equipment and will be fully instructed on it's use before the dives!

It sounds like an accident waiting to happen.

However the literal answer to your question is that you could go to 185fsw and not incur deco if you went straight down there, stayed there for a minute, and came straight back up to the shallows.

 

[divebunny13]

Hi all,

I can answer some of the questions about our diving, but I don't do the tech diving so I'll have to get someone else to answer the technical questions.

Our Over the Wall dive has been one of our signature dives for 50 years. We descend over the Tongue of the Ocean and sit on a ledge at 185 feet. From the time we leave 20 ft until the time we have to LEAVE 185 and start ascending we have 5 minutes. The rest of the dive is spent at 55 or so. The total dive time is 18 minutes and when time correctly, is a no deco dive. It's led by a team of divemasters and we control time and depth. Like I said in the Spiegel thread, I've been doing this dive for two years and have never had an OOG situation.

As far as Church Windows (225ft) and some of the inland blue holes, they do dive on AL80s but they carry extra gas and have stage bottles.

The deeper dives and cave dives are done on a case by case basis after spending time with divers to evaluate their skills.

Whoever recommended Brian Kakuk for caving was right on. He's a friend of Small Hope's and dives our caves here. We've got an awesome cave survey that he did of one of our Blue Holes on the wall in the Lodge.

If you're a diver that like to stay within recreational limits, we've got plenty of great dives for that too! Over 60 dive sites within 15 minutes and only a few are below recreational limits.

 

[UCFKnightDiver]

Both those dive plans are at best irresponsable and reckless, and at worst suicidal in my opinion. 225 in a cave for non trainined divers using single 80's on air? holy shenanigans

 

[ianr33]

Both those dive plans are at best irresponsable and reckless, and at worst suicidal in my opinion. 225 in a cave for non trainined divers using single 80's on air? holy shenanigans

What could possibly go wrong? Its lead by a team of divemasters silly.