Cozumel Incident 9/4/11

[Kymcobob]

Crush, you are right, it was a lousy analogy. You are tired of the apologists, I was tired of the serf-righteous whiners claiming this event is going to ruin Cozumel. And thanks for the welcome, I'll be there next week to enjoy some underwater time.

 

[MMM]

I was tired of the serf-righteous whiners claiming this event is going to ruin Cozumel.

The only way this story could have negatively affected Cozumel would have been if the monster vertical downcurrent story on another thread had developed any traction. Fortunately that has been put to rest.

Nauticab, thanks for posting your thoughts below regarding captain's responsibilities. I hadn't heard of anyone hanging tanks off the boat but then I'm one of those who likes to dive with steel tanks and the extra air they afford. It's hard to believe that Gabi was doing this kind of diving if he had been bent once already. I would have thought it was contraindicated.

I've walked past your shop a few times but never stepped inside. I will next time I'm down this winter and introduce myself.

a 2nd doctor told him it will be best to NEVER dive again since he was bent before (not sure of the extent or type or symptoms)....since if he dove again, he would be playing with his life.

with regards to captains and their role (something not discussed here...what was the capt doing? and why did he allow a IWR dive?):
more training for the captains as to signs of DCS.
giving the captains the AUTHORITY OVER THE DM for redundancy of equipment if a planned deep dive, with a tank hanging at 60', etc etc. (i now of dive ops that have a tank or 2 hanging at 60' whenever there is a punta sur dive).
also giving the capt auth OVER THE DM to tell them NO for an in water recompression and insist on chamber treatment (or at least evaluation) immediately. it shouldn't matter if it was the boss wanting to do it.

 

[sealkie]

with regards to captains and their role (something not discussed here...what was the capt doing? and why did he allow a IWR dive?):
more training for the captains as to signs of DCS.
giving the captains the AUTHORITY OVER THE DM for redundancy of equipment if a planned deep dive, with a tank hanging at 60', etc etc. (i now of dive ops that have a tank or 2 hanging at 60' whenever there is a punta sur dive).
also giving the capt auth OVER THE DM to tell them NO for an in water recompression and insist on chamber treatment (or at least evaluation) immediately. it shouldn't matter if it was the boss wanting to do it.

I have wondered how much pressure may have been on the staff involved in this incident given the boss was one of the divers. I would expect there would have been little protection extended to a captain or DM who stands up to a dive shop owner and gets fired.

 

[Rescue Diver68]

I have wondered how much pressure may have been on the staff involved in this incident given the boss was one of the divers. I would expect there would have been little protection extended to a captain or DM who stands up to a dive shop owner and gets fired.

I can assure you that this is not the case as no one at this dive op creates or operates under that type of (cut-throat) working environment.

 

[Ron Lee]

This is from Jim Lapenta in Post #34

8 minutes:
Decompression model: VPM - B

DIVE PLAN
Surface interval = 1 day 0 hr 0 min.
Elevation = 0ft
Conservatism = + 2

Dec to 200ft (4) Air 50ft/min descent.
Dec to 300ft (5) Air 60ft/min descent.
Level 300ft 2:20 (8) Air 2.12 ppO2, 300ft ead
Asc to 140ft (13) Air -30ft/min ascent.
Asc to 90ft (14) Air -30ft/min ascent.
Stop at 90ft 1:00 (16) Air 0.78 ppO2, 90ft ead
Stop at 80ft 2:00 (18) Air 0.72 ppO2, 80ft ead
Stop at 70ft 2:00 (20) Air 0.65 ppO2, 70ft ead
Stop at 60ft 1:00 (21) Air 0.59 ppO2, 60ft ead
Stop at 50ft 3:00 (24) Air 0.53 ppO2, 50ft ead
Stop at 40ft 3:00 (27) Air 0.46 ppO2, 40ft ead
Stop at 30ft 5:00 (32) Air 0.40 ppO2, 30ft ead
Stop at 20ft 6:00 (38) Air 0.34 ppO2, 20ft ead
Stop at 10ft 10:00 (48) Air 0.27 ppO2, 10ft ead
Surface (48) Air -30ft/min ascent.

Off gassing starts at 138.3ft

OTU's this dive: 28
CNS Total: 436.1%

85.5 cu ft Air
85.5 cu ft TOTAL

I finally seem to have a grasp of what it is showing and this version (of three posted) seems like a reasonable plan. Perhaps it is a minute too long at depth but seems close had nothing gone wrong. It would be nice to see how the gas requirement changes with a 400' bottom.

If the assumed air consumption rate is close for the woman and DM, then they started out with too little gas. 120 cu ft tanks may have helped substantially.

That makes me wonder how much experience they had deep. Surely they must have had some experience in the 250-270' range to know how they would react to nitrogen and that they had plenty of air. I don't see someone with only knowledge of how they react at 130' suddenly deciding to go to 300'.

If they did have enough exposure at 250'-270' to know that going a bit deeper may not have increased the risk dramatically...and IF people react about the same to nitrogen under similar conditions, what is the likely explanation for one diver apparently becoming narced and slowly descending or swimming deeper?

A second issue was the site. Further south are sites that have sloping bottoms. My view is that doing a risky dive in that area may have been better. Should a diver become narced, "maybe" they will just drop a few feet and hit the sloping ocean floor. That would make a rescue far easier. I don't know if this sloping characteristic applies at 300'. Most likely it does to at least 250' in some places.

This is not a tutorial on making 300' dives on air. On the continuum of safety for a 300' dive, where on one end you have two divers who come out of Devil's Throat and decide to drop to 300' to the accepted way of doing a 300' (gas mixture, equipment, support, pre-planning ,etc), this dive was not on the safe side of that continuum. It could have been better.

I still believe that in time a release of the dive computer data by at least one of the people who ended up around 400' will be useful. The bad outcome may discourage some deep diving but I doubt that it will end. A complete airing of the events will hopefully prevent a recurrence. I had no desire to dive to 300' on air before this. That is reinforced by the serious medical problems encountered.

 

[boulderjohn]

This is from Jim Lapenta in Post #34
I finally seem to have a grasp of what it is showing and this version (of three posted) seems like a reasonable plan. Perhaps it is a minute too long at depth but seems close had nothing gone wrong. It would be nice to see how the gas requirement changes with a 400' bottom.

Here's how you can figure it out. I am posting this so that anyone reading it can estimate the danger of doing this kind of dive without planning for this kind of a contingency.

First of all, Jim's V-Planner schedule assumed a pretty good RMV (Respiratory Minute Volume, sometimes called SAC Rate), the rate at which the divers would have been consuming air if they were at the surface. (I know because I made such an assumption myself and came up with a similar plan.) There is a good chance that these highly experienced dive guides might do a bit better.

However, if one diver gets narced at 300 feet and descends swiftly to 400 feet with another in fast pursuit, the RMV shoots up because of the effort. In contingency planning, many tech divers assume that in an emergency their RMV will hit 1.0 cubic feet per minute in such an emergency. That 1.0 RMV becomes our starting point.

Let's say that they did a swift 100 FPM descent from 300 feet (1 minute) and perhaps a 60 FPM ascent to 300 feet. Give them a relatively rapid turnaround at 400 feet, and we are looking at maybe 3 minutes total time below 300 feet. So if we multiply 1.0 Cubic feet per minute by 3 minutes, we get 3.0 cubic feet used if they were at the surface.

Now let's figure it out for that depth.

Every 33 feet of sea water equals an atmosphere of pressure. Given the turnaround time at the bottom, their average depth would have been roughly 11 times that (363 feet). Add 1 atmosphere for the atmosphere itself, and they were under about 12 atmospheres of pressure during those three minutes. So we multiply the 3.0 cubic feet times 12 to get 36 cubic feet used in those three minutes at that depth.

An AL 80 tank filled to 3,000 PSI holds 77.4 cubic feet of air. That brief excursion to 400 feet would have used nearly half of it.

 

[ianr33]

Something else I have been thinking about.

When I first started doing deepish dives I was very surprised by how long it takes to stop a descent. Pressure is greater,gas is denser and it seems to take forever to fill a BC.

Easy to imagine someone dropping at 100'/minute (which they would need to do given the tiny gas supply) Hitting the brakes a bit late,quite possibility due to disabling narcosis, and sailing past the planned 300' down to 350+

As John pointed out above,that extra 50 feet will totally mess up the gas planning.

 

[Brules]

What a tragic and unfortunate set of events.

My take away from all 41 pages has been: Just because you are a diver or DM with thousands of dives, it does not make you a technical deep diver. Dive your certification, if you want to push the envelope, study, train and prepare for it. This process/accident could be easily transposed to 3 non cave divers saying "hey, lets go in that cave".....the actions taken after the dive surely (IWR) compounded the seriousness of the injuries.

Sad it happened to such good people. I hope they make a full recovery. Even with proper training, preperation etc - a dive to that planned depth is extremely dangerous, and once Murphy shows up - it becomes even more dangerous.

 

[Texas Torpedo]

Something else I have been thinking about.
When I first started doing deepish dives I was very surprised by how long it takes to stop a descent. Pressure is greater,gas is denser and it seems to take forever to fill a BC.

I bet! Especially when you dive 2x Faber 108's.. Might take a full AL80 to stop those bad boys at depth..
Joking aside, you make a good point.. If all the metrics were known, I'm sure one of the mathematicians here could come up with required (wasted) gas to neutralize the decent.

 

[fdog]

I bet! Especially when you dive 2x Faber 108's.. Might take a full AL80 to stop those bad boys at depth..
Joking aside, you make a good point.. If all the metrics were known, I'm sure one of the mathematicians here could come up with required (wasted) gas to neutralize the decent.

<<Disclaimer: what follows is entirely supposition on my own accord. I am posting it in the hope that someone will see this, and sit down with a thump, and seek out a good class in Rock Bottom. I have not recieved any of the magic PM's, or had any inside information, and I extrapolated this from what's been posted (and my first-hand observations of divers under duress).>>

Dive starts. Three divers with full Aluminum 80's of air.
0 cf used
78 cf remain


Divers are very experienced, and quickly descend to 300' at a fast rate of 100 fpm.
3 minutes dive time
15 cf used
63 cf remain


Since the divers are wearing 3 mil suits, the have to add air to their BC's to get neutral.
1 cf used
62 cf remain


An emergency occours that places one diver at 350'. A second diver gives chase. This leads to an elevated RMV - say, 1 cfm, being generous - and it takes 1 minute to chase, 1 minute to resolve the emergency, and both divers (breathing their own backgas) begin swimming up the emergency to a depth of 270'.
7 minutes dive time
44 cf used
18 cf remain ...This is 700 psi at 270 feet...


The pair meets diver #3. Because they are well-trained in decompression, they remember that in their original plan they must get above 113' quickly. With the "OMG" moments behind them, their RMV decreases a bit to 0.75 cfm, and they swim up to 130' at 50 fpm.
10 minutes dive time
15 cf used
3 cf remain


The pair exhausts their gas, and begin breathing from diver #3, who avoided getting wrapped up in the emergency, and thus fortunately has 26 cf remaining for the team.


The pair has 29 minutes deco obligation at this point; diver #3 has only 23 minutes obligation. With only 8.5 cf per person, and struggling to buddy breath while ascending, the best the trio can do is slow their ascent to 30 fpm.
14 minutes dive time
25.5 cf used
0 cf remain



...Of course, this is the best case scenario, where the pair exhausts their gas during the ascent. The worst case involves the pair sharing air at 350'.


This is all a work of fiction, but I hope someone learns from it.


All the best, James

At the risk of being labeled "nerd boy", it actually figured out at 1.26 cubic feet.


All the best, James