Fiona Sharp death in Bonaire

[Dan]

The way you select a mix for such a dive is ensure you can drop the ppO2 of the loop during a flush, which means a dil ppO2 at target depth of about 1 bar and the target END to select the proper fHe.
In a dive like the one reported I would have selected 8/70 It also depends upon my offboard bailout which I can plug in the loop as an offboard dil.

I am wondering if it is known what was in the s40s: she might have had different gases. In such profiles I have multiple gases which I have programmed in my computers and I have the flexibility to plug all in the loop. But for that depth I bring down 3 s80 (10/60 30/30 50/20) and a s40 100% oxygen (also pluggable in the loop). So she was not self sufficient for a 100 mt dive IMHO no matter what bottom time she planned. Especially because she could not descend fast.

This kind of diving is way beyond my risk acceptability level (no solo below normoxic range). Below 80 m I want a team (3 better than 2) one with the issue one helping and one managing depth, deco and gases.

My 2c

Thank you for such detail CCR dive plan to 300' depth. From @tursiops comments, below,

I am in Bonaire. I was on the dock while she was setting up. Inspiration, two AL40s. I did not see if they were plumbed into the BOV or not. She suited up, took the the two bottles, dropped them in, put her RB on, and entered the water. She did not prebreath on the dock, but may have in the water.....she remained face down at the surface for a while after she donned the two 40s, and then swam off. Nice, friendly, outgoing lady. I was told staff saw her face down on the reef at 25m. There was some confusion because a Rescue class was going on at the same time, and apparently some who saw her thought she was part of that class.

Well, 300 ft is confirmed, by head of tech ops at Buddy Dive. Worse, the dive was on air diluent. Jeez. One word: complacency. There are no other words for this type of pushing one's limits.

It seems to me that diving down to 300' was not on her plan. Some unplanned thing happened that made her lose one of the AL40's and dove to 300'.

Spoke to one of the staff who brought her up. She had just one 40 on her, on the right side. Separate info, which is second-hand info, was that the two 40s were air and 80%. If so, presumably the 80% was on the right/rich side, suggesting the 40 of air was somehow lost. Most confusing. Something clea

 

[PT4476]

If the reports regarding diluent and bailout are accurate I agree that it is unlikely that a 90m dive was her plan.

 

[Dan]

The missing 40 is concerning and may explain the deep dive. Perhaps it was dropped and an attempt to retrieve it was made. Assuming the info we have so far is correct and data was gathered from her computer.

It would be great to see the dive profile. How quickly she went to 300' and what was her bottom time at that depth.

Is it possible to make a quick dip to 300' with such gear set up and survive to tell the tale?

 

[PT4476]

It would be great to see the dive profile. How quick she went to 300' and what was her bottom time at that depth.

Is it possible to make a quick dip to 300' with such gear set up?

Possible, yes, but a very bad idea. No one I know with the training to to dives in the 300' range would consider it.

 

[Vicko]

Dilutent would be no more than 13% oxygen and no less than 50% Helium, most people would use something like 10/60 for dilutent.
For bailouts we usually rent out 10/60 for bottom but people like their bottom bailouts to be Helium rich. You would definitely use a lot more than 2 40cf tanks. Something lie a full 12L steel at 250 bars bottom (12/50), 11L travel (20+/30) and 11L deco mix with o2 on the line, if no surface support than a 7l of O2 would be reasonable.

 

[Kay Dee]

For the experienced CCR diver, diluent gas mixes (and bailout for that matter) for that depth are a personal choice and not set in stone. While air is out of the question, ideally the partial pressure of oxygen in the diluent should not be more than 1.4 bar/ata (at max depth) and the narcotic effect of the nitrogen content to, again ideally, not be more than a 30m / 100ft equivalent air depth (at max depth). Of course, people do deviate from those diluent recommendations, generally by lowering them, i.e. being more conservative for both oxygen levels and narcosis effect. But some may even raise them.

As someone else noted though, an experienced CCR diver on air (diluent) chasing a droped cylinder to 90m would / should be highly unlikely (but IMO not out of the realms of possibly happening). I have seen a CCR diver upon surfacing, then chase something much less valuable to almost 70m (and get bent for his trouble).

 

[tursiops]

Update

Both 40s were on her. One was removed, dropped, recovered, by another member of the recovery team.
The 40s contained 80% (untouched, still full) and 20/20, NOT air as previously reported second hand.
Dil was air.
Handset showed 91m.

 

[Wookie]

Update

Both 40s were on her. One was removed, dropped, recovered, by another member of the recovery team.
The 40s contained 80% (untouched, still full) and 20/20, NOT air as previously reported second hand.
Dil was air.
Handset showed 91m.

It seems to me, not a rebreather diver, but been around plenty of them, that every bit of gas for this dive is completely inappropriate.

Air dil
40 cf 20/20 BO
And 40 cf 80% for her offboard O2.

She had made no provision if anything happened to her rebreather. She couldn’t use offboard gas to plug in in the event of a gas failure, and wasn’t carrying enough for bailout.

Am I missing something?

 

[The Chairman]

Unfortunately, dives are often planned for everything to go well. Dive after dive reinforces the lie that this is an acceptable idea... until something goes horribly wrong. Hope for the best, but plan for the worst. The opposite is not always survivable.

 

[Kay Dee]

It seems to me, not a rebreather diver, but been around plenty of them, that every bit of gas for this dive is completely inappropriate.

Air dil
40 cf 20/20 BO
And 40 cf 80% for her offboard O2.

She had made no provision if anything happened to her rebreather. She couldn’t use offboard gas to plug in in the event of a gas failure, and wasn’t carrying enough for bailout.

Am I missing something?

What are you missing? Not much.

However, some CCR divers will run a hot bailout on the premise that should they have to bail at max depth they will bolt up to where the mix would be 1.6 ppO2 (or less). In this case that would be an ascent covering a vertical distance of 20 odd metres, which IMO would be a bit much (but in the 'comfort' zone as it were for some divers).

Another thing to note is that some CCR divers only carry enough bailout to complete their deco up to (an event happening) about midway - or less - through their dive; working on the premise that if anything goes wrong with the 'breather then it will do so at the beginning or soon after on the dive (which is often the case).

Not advocating either practice, just saying is all.

It's the air dil that is truly worrying.

The 'unknown known' it seems now is her time at max depth.