What would you have done? Cave diving incident

[graham_hk]

,,,

[Tibbs78]

I am making no suggestions as to how the situation should best be sorted as I know that I am in no way qualified to comment on anything specific to tech diving or cave diving.

I will leave that to those with more training and experience.

I might just go and look for Gareth's book - it sounds like a very worthwhile read.

It should be mandatory reading for all divers, IMO. I've done a full read but need to go through chapter by chapter to fully get the benefit. It's the most important book about dive safety since Sheck's Blueprint for Survival.

[Mikael]

Is there any possibility now that you have returned from the trip that all four divers could meet up expressily for the purpose of discussing what happened in to learn from it and air feelings in an open considerate way?

Even if you never dive with some or any of these individuals all four of you could learn more. If you do dive together again then by having a sit down well ahead of time you are more likely to all be on the same page meaning feel less pressure in the run up to the next dive which in turn shoud mean a more thorough breifing.

Once you have talked you could then go out for a beer or two as to make it fun as well.

[t0by]

It's not fun when you want to turn a dive and your companions aren't around. I think it's best to leave the cave as soon as you reach the edge of your comfort zone or gas limits. Perhaps leaving a marker with the words 'Left Cave' written on.

[Tibbs78]

Is there any possibility now that you have returned from the trip that all four divers could meet up expressily for the purpose of discussing what happened in to learn from it and air feelings in an open considerate way?

Even if you never dive with some or any of these individuals all four of you could learn more. If you do dive together again then by having a sit down well ahead of time you are more likely to all be on the same page meaning feel less pressure in the run up to the next dive which in turn shoud mean a more thorough breifing.

Once you have talked you could then go out for a beer or two as to make it fun as well.

I spoke at length to my main buddy, and also briefly to Diver C. I will have a longer chat with C as well as we have some stuff to clear up.

I also need to apologise to Diver D for putting them at risk by staying so long.

[Steve Clark]

In cave diving we have 2 'turn' signals. The finger twirl is the signal for, let's go home, slightly faster than we went in (as you should) but we can still sight see/film/whatever (opinions vary as to exactly what). A classic thumb means 'let's get 0the hell out of here' no sightseeing, no nothing, and swimming quickly.
All the divers on the dive knew this.

This is interesting. I use both these signals in the teams I dive with, but don’t attribute the same meanings. (GUE Cave 2).

The thumb is turn. Normally when someone hits gas, or reached where we want. It’s very deliberate. The whole team sees it and we are very careful with direction when turning the team. We exit the cave in the normal way.

The spinning finger only really gets used when we are poking around down jumps, or are going back to a T to try the other branch. All within gas limits.

I’m not a fan at all of on-the-fly recalculating gas in the water. I will do it on the surface with the same set for another short dive (keeping a min time reserve for a shallow dive too.) I will do it in a sink/gap on the surface on a big traverse. I will also dive beyond thirds of total gas on a working/survey dive, with 4-5x known exit gas. In water, eating into your original 3rds plan to get a few more minutes bottom time. Not for me. You might be lost and just not realised yet!

(If it’s any consolation, I’ve finished a cave dive with no actual failures and 3 GUE buddies, with 10bar in my back gas. It’s easy to be confident and get it wrong.)

[JonG]

Huge caveat here in that I am new to the OHE! First off though thanks for sharing it takes guts to air these things in public.

I would have turned on my pressure but I am more of a solo diver than a team diver and would have made clear that given the mixed nature of the team first principle would be to look after yourself in the event of an incident/issue, but also to plan and manage gases on this basis, which can/could include additional stages or buddy bottle for this eventuality.

Its not clear from the narrative but it looks as if you were using half plus 20 in the stage, but thirds on back gas, I thought/think the protocol when using half plus is to remove the volume of gas used from the stage from the backgas total volume before calculating thirds? This gives you back the margin of safety that going beyond thirds in the stage removes and places the reserve on your back where it is arguably more useful, because you can drop the stage to improve speed on exit.

I might have misunderstood the plan though.

It does also seem like a bit of a complex/loose plan which I would feel more comfortable completing on RB as opposed to OC. On OC I like to be very definite about the route, jump lengths etc. and aim for a simple linear route that gives a feel for times/gas consumption, that way if starts to drift from the expected flags start to come up early. It sounds like your route was in, branched jumps, back, re-calc then back in(?). I would have gone to end of gas reserves (half plus and revised third on back gas or thirds in back gas and stage) and then out. The out may have been shorter than the in (with it's branches) but adds a safety margin, plus you retain the gas spread across the doubles and the stage for extra redundancy.

As the only doubles diver, theoretically you were the one at greatest risk in the event of separation from the SM divers, SM is seen to be safer if correct gas management protocols are followed because of the total independence of the breathing sources. This may have been in their heads encouraging more of a solo mentality, even if only subconsciously. If you had lost an LP hose, manifold failure etc. depending on the speed of response you could have lost enough back-gas to put you at risk of not making the exit esp as the stage had been emptied and dropped (?). Given the mixed nature of the team on doubles I would have had a sacrificial bailout option unless it was very clear in the planning that this risk was present and therefore mitigated by team cohesion.

My maths isn't good enough top side to risk recalculating thirds part way through a dive underwater so I avoid this like the plague!

I havent read Gareths book but do often refer to cavediving.com which is a really useful resource and emphasises the need for clear planning, simple route options, etc.

As others have said though prior agreement of the plan, eventuality planning, signalling are critical especially if the team is large as this was, but it's easy for me to critique it all from the comfort of the living room!

Got a weekend with a mixed pair coming up (RB/OC) so will see how well my theory matches with reality!

[WFO]

Yes indeed, 3 in a team is my maximum, 2 in some caves I've been in. I will reiterate what that means to me the next time I'm diving with more in the water.

How would you have handled the situation?

I wouldn't have been in it because... (and I can't fkin believe noone has said it yet) .... you should have been on a rebreather.




Hindsight is 20-20. I don't know what I would have done, I'd like to say "well I'd have not been in that situation in the first place because I've never ever got in the water with a slightly less than perfectly planned and briefed team" which is clearly bollocks.
Also it's dead easy to say "well you should have left at turn pressure and screw diver A", which was probably the right course of action but hey, you didn't know that at the time.

I think it was probably a mistake on your part to wait past your turn pressure, as at that point you are becoming less and less of a help to anyone else in there and more of a liability. If they had a problem getting back through the restriction you wouldn't be any use to them, as you had no gas.

As for yelling at people, well you chose to sit there.

Personally I'm all about the solo mentality even if you're diving with people.

[Steve Clark]

Its not clear from the narrative but it looks as if you were using half plus 20 in the stage, but thirds on back gas, I thought/think the protocol when using half plus is to remove the volume of gas used from the stage from the backgas total volume before calculating thirds? This gives you back the margin of safety that going beyond thirds in the stage removes and places the reserve on your back where it is arguably more useful, because you can drop the stage to improve speed on exit.

I might have misunderstood the plan though.

That is the general principle.

As I understand it in this case, I think they returned to the entrance and dropped the (now empty) stages. From this point it is a standard/'new' 3rds dive.

[Tibbs78]

That is the general principle.

As I understand it in this case, I think they returned to the entrance and dropped the (now empty) stages. From this point it is a standard/'new' 3rds dive.

Yes indeed. The gas planning was as follows:

210 bar everywhere.

Stage - dropped on half plus 15bar @120bar = 90bar pen

45 Bar off 210 Bar twinset = 165 bar effective starting pressure

1/3s on 165 bar = 55 Bar penetration

210 - 55 = 155 Turn Pressure

Round up to 160 bar for ease of reading

2 numbers to remember: Drop on 120, turn on 160.

I exited on 140 bar back to the start and then dived thirds on the 2nd half, 40 bar in & out leaving 60 bar at the end of the dive

[t0by]

Yes indeed. The gas planning was as follows:

210 bar everywhere.

Stage - dropped on half plus 15bar @120bar = 90bar pen

45 Bar off 210 Bar twinset = 165 bar effective starting pressure

1/3s on 165 bar = 55 Bar penetration

210 - 55 = 155 Turn Pressure

Round up to 160 bar for ease of reading

2 numbers to remember: Drop on 120, turn on 160.

I exited on 140 bar back to the start and then dived thirds on the 2nd half, 40 bar in & out leaving 60 bar at the end of the dive

I don't understand why people take this approach to gas planning. It feels so complicated. Perhaps with manifold tanks it makes sense, but surely not with independent tanks(I did a dive with Lanny like this a while ago)

I just dive everything to thirds. Or quarters if it's a scary cave.

[graham_hk]

...

[JonG]

Yes indeed. The gas planning was as follows:

210 bar everywhere.

Stage - dropped on half plus 15bar @120bar = 90bar pen

45 Bar off 210 Bar twinset = 165 bar effective starting pressure

1/3s on 165 bar = 55 Bar penetration

210 - 55 = 155 Turn Pressure

Round up to 160 bar for ease of reading

2 numbers to remember: Drop on 120, turn on 160.

I exited on 140 bar back to the start and then dived thirds on the 2nd half, 40 bar in & out leaving 60 bar at the end of the dive

That makes more sense, just couldn't quite pick up the strategy from the original post.

[JonG]

relevant thread on various stage approaches for reference:

https://www.scubaboard.com/community/threads/my-stage-diving-strategy.570672/

[t0by]

Because if you dive thirds in the stage you are leaving reserve gas in the stage rather than back gas and therefore exceeding thirds on your back gas at worse point of dive (at end of penetration) ...

Ok, so is the assumption that you need to plan for your stage not being there when you need it?