Two German divers drown at Gran Cenote Kalimba at Tulum

[1atm]

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3. Going against the flow and filming inside Much's Maze while returning was what really messed up their plan in terms of gas use on the way back..

This is probably one of the biggest factors in this accident. Not only the flow, but filming also, so spending significantly more time and gas on the way back than what the gas plan would dictate ...

 

[Hiszpan]

There’s one more - highly speculative - option: one of the divers turned on thirds, the other didnt check and was already beyond thirds. It might happen if say diver A usually has better consumption than diver B, so A gets into the habit of waiting for B to turn, assuming that A himself will have more gas. If for whatever reason on the day, A uses more than B (or started with less), by the time B turns, A will have gone beyond thirds. If B was a tiny bit late to turn (psychology of always being the first to turn), then both went beyond thirds ...

This is what I thought when I wrote my first post here, after reading the excellent report by Izzy. Whether it happened or not, it makes me want to change the way I dive by actually checking the air of my buddy at the turn as opposed to just accepting his "turn" sign. Prevention is better than a cure.
Whether my usual cave diving buddy (20 times more experienced in caves than me) accepts that or not, remains an open question...

 

[Hiszpan]

This is probably one of the biggest factors in this accident. Not only the flow, but filming also, so spending significantly more time and gas on the way back than what the gas plan would dictate ...

My last cave dive that I mentioned in that post, we were supposed to, on our way out after reaching the stages, replace a line in the cave as it's a bit overgrown with stuff. I wasn't 100% cozy with that plan, as this dive was quite complex for me and we visited a part of the cave on it that I never went to. When we got to the reel that we left to use to replace the line, to my relief my buddy signalled he's cold and we proceeded straight to exit. Whether this was true or he changed his mind during the dive I will never know.
During the debrief I suggested next time to plan any "activities" only on our way in, as that would make me much more comfortable during the dive. He agreed.

 

[CptTightPants21]

This is what I thought when I wrote my first post here, after reading the excellent report by Izzy. Whether it happened or not, it makes me want to change the way I dive by actually checking the air of my buddy at the turn as opposed to just accepting his "turn" sign. Prevention is better than a cure.
Whether my usual cave diving buddy (20 times more experienced in caves than me) accepts that or not, remains an open question...

I can understand this sentiment, but if that is the level of trust in the other diver and his abilities that you have; what the hell are you doing in a cave with that person?

If I had a dive buddy that demanded to check my pressure gauge after every turn we simply wouldn't be doing many if any more dives together. I have to deal with a lot of overbearing in the real world, I sure as 5h1t am not dealing with that when I am under water.

 

[Scuba Lawyer]

I really appreciate seeing the report. I have replayed that dive (Calimba-Gran Cenote) many times in my head. It's been a few years so my recall is fuzzy. Can't recall the transition from the Calimba passage to the Gran Cenote main line. Seems like there was a jump from Calimba line to an intermediate line, then to the Gran Cenote main line. I recall (from two decades ago) we would make a morning dive entering Gran Cenote, install the jump line to Calimba, then exit Gran Cenote. In the afternoon we would enter Calimba and exit Gran Cenote, removing the jump line behind us. We did the Box Chen loop for our full cave graduation dive, entering and exiting Gran Cenote with two stage bottles. Very much a "trust me" dive but our instructor mapped it out well for us and we had enough back-gas to reverse course to our stage bottles should anything untoward happen to him on the dive. Good memories. So sad it appears this incident was a simple gas management issue.

 

[Hiszpan]

I can understand this sentiment, but if that is the level of trust in the other diver and his abilities that you have; what the hell are you doing in a cave with that person?

If I had a dive buddy that demanded to check my pressure gauge after every turn we simply wouldn't be doing many if any more dives together. I have to deal with a lot of overbearing in the real world, I sure as 5h1t am not dealing with that when I am under water.

I trust him, but mistakes happen inadvertently.
Plus, if I remember correctly, we actually exchanged our pressure readings at the turning point anyway. I just didn't think it could go wrong in that way and will now keep that extra detail in mind.

 

[kafkaland]

I really appreciate seeing the report. I have replayed that dive (Calimba-Gran Cenote) many times in my head. It's been a few years so my recall is fuzzy. Can't recall the transition from the Calimba passage to the Gran Cenote main line. Seems like there was a jump from Calimba line to an intermediate line, then to the Gran Cenote main line. I recall (from two decades ago) we would make a morning dive entering Gran Cenote, install the jump line to Calimba, then exit Gran Cenote. In the afternoon we would enter Calimba and exit Gran Cenote, removing the jump line behind us. We did the Box Chen loop for our full cave graduation dive, entering and exiting Gran Cenote with two stage bottles. Very much a "trust me" dive but our instructor mapped it out well for us and we had enough back-gas to reverse course to our stage bottles should anything untoward happen to him on the dive. Good memories. So sad it appears this incident was a simple gas management issue.

Wow - double staging for your full cave graduation dive? That would be unusual for most agencies, unless you did something like C2, which is a bit more than full cave.

 

[Scuba Lawyer]

Wow - double staging for your full cave graduation dive? That would be unusual for most agencies, unless you did something like C2, which is a bit more than full cave.

Three of us took a 10 day zero to hero course in September 2000. Steve Gerrard was our instructor. We started the course with 1000's of dives and open water instructor certs in our backgrounds. Of course we learned quickly that none of that experience amounted to diddly squat in the cave environment. The point I'm making is that we were very comfortable in the water and Steve said he sensed that early on. He pushed us harder than he would most students and we ate everything he threw at us up. We were going from 7 am to 11 pm every day with book work even during mealtimes. It was very intense. He started adding a single stage on our dives on day 6 and by the last two days we double staged. I started the course thinking I knew everything and graduated knowing I still only knew a fraction of what I could know. We got full cave cert cards from NACD, IANTD and NSS-CDS. One of the best 10 days in my life!

 

[barth]

What kind of gasplanning would diverse use for this dive?

When I would start with 210 bar in my doubles (or two side mount tanks) and 210 bar in my stage I would start the dive with my bottom stage. I would drop the bottom stage at the line at 110 bar.

Backgas I would reserve gas for my bottom stage, if it would be lost or a failure. That means 210-50 bar =160 bar backgas left.

In a team of 3 I would use 1/3 of my backgas for penetration. That means 50 bar for penetration (160 bar/3). Turnpresure would be 210-50 = 160 bar.

In a team of 2 I would use 1/4 for penetration.that means 40 bar (160bar/4). Turnpresure would be 210 -40 = 170 bar.

Are there divers who would use 100 bar of their bottom stage and drop it on the line and would also use 70 bar backgas for penetration in a team of 2 divers ?

 

[rjack321]

I can understand this sentiment, but if that is the level of trust in the other diver and his abilities that you have; what the hell are you doing in a cave with that person?

If I had a dive buddy that demanded to check my pressure gauge after every turn we simply wouldn't be doing many if any more dives together. I have to deal with a lot of overbearing in the real world, I sure as 5h1t am not dealing with that when I am under water.

I ask my buddies "how much gas you got?" fairly regularly actually (once or twice a dive at critical junctures mostly). Its no different than asking "wanna take this jump?" or something like that. Hard to be on the same page on a dive if you dont share information both - hard info like gas and soft info like "stick to the mainline here?" or "this is smaller than I want"

I don't think asking "ok on gas still?" has anything to do with trust at all - at least for the people I dive with.