Question Do we have viable alternatives to Shearwater?

[inquis]

what would be a good thing for the computer to display when the model is (as a very reasonable supposition) wrong

IMHO, display a "Ceiling Violated, xx% GF99" warning post-dive with the maximum GF99 incurred and leave it up to the user to gauge the severity. It's a tool, not a babysitter.

 

[JMarc]

Yesno: you're over the M-value and are no longer "safe" but it can still track your gas loading.

It is tracking some values. How they are related to tension when the overstep is big enough to offset all the safety margin is an open question.

@David Carron's question, what should a computer do when going outside of the acceptable parameter range of the model, is important. And there is a lot of possibilities between nothing and brick the computer for the smallest overstep. Not liking the latest do not force to chose the former.

Note that building a more accurate model is not really an answer, as David question is relevant whatever the model used is.

 

[Wibble]

Note that building a more accurate model is not really an answer, as David question is relevant whatever the model used is.

The fact is we're random fleshy human things with all sorts of stuff going on inside our skin. All decompression algorithms are just that, algorithms which sort of statistically match the desired outcomes; not getting bent.

There's many people with odd physiological issues which mean they're more susceptible to being bent; for them the standard algorithms need to be amended to be vastly more conservative.

On several boats I've been on over the years, a handful of divers have succumbed to DCS despite following a perfectly normal dive profile and ascent.

• A couple of divers have had an undiagnosed PFO (hole in the heart), almost the most common reason for DCS. One of these had 5 days of recompression chamber treatments
• One was hospitalised for a couple of days due to heart issues (high heart rate), oddly at the end of a week's deep diving which may have had something to do with it.
• Another had a skin rash following a deeper dive, but was fine doing shallower deco dives. They spent the trip back breathing high PPO2 from their rebreather which settled things down.

Cannot help but wonder if dehydration is an issue on long dives. The second most significant invention for scuba diving is the pee valve; no need to be worried about drinking plenty of water before a dive.

Anyway, the algorithm doesn't take into account someone's physiological issues.

 

[dmaziuk]

It seems likely that the situation is worse than that. If you exceed your "m value" ZHL16 will certainly point that out, but as soon as you redescend ZHL16 will not only forget the whole thing but will reward you by reducing your decompression time.

I think the real problem is that the symptoms can take a while to develop. If it were instantaneous, there wouldn't be a question what to do: you'd be bent and wanting to get to the chamber fast. As it is, a clueless diver could do what you describe, develop symptoms an hour later, and blame the computer for the "undeserved" hit.

FWIW I always thought by branching out into "recreational" market Shearwater put itself one clueless diver away from a lawsuit, but that's their business.

 

[David Carron]

I think the real problem is that the symptoms can take a while to develop. If it were instantaneous, there wouldn't be a question what to do: you'd be bent and wanting to get to the chamber fast. As it is, a clueless diver could do what you describe, develop symptoms an hour later, and blame the computer for the "undeserved" hit.

FWIW I always thought by branching out into "recreational" market Shearwater put itself one clueless diver away from a lawsuit, but that's their business.

So what do you think might be an appropriate response from a dive computer in one of these cases? As pointed out by @JMarc above, not liking one extreme does not necessarily impose the other.

 

[dmaziuk]

So what do you think might be an appropriate response from a dive computer in one of these cases? As pointed out by @JMarc above, not liking one extreme does not necessarily impose the other.

There isn't one: you can "gracefully degrade" into showing them their gas loading after they're bent, or you can "fail safe" into displaying "get to da chamber" message for 24 hours, but neither is inherently better or worse than the other. You might as well flip a coin, or let the Legal Dept. decide.

 

[BoltSnap]

How long have you been using Ratio?

Since 2017. I bought my first iX3M in 2017, and I upgraded it to the iX3M2 a few months ago.

Have you ever contacted their customer service for help?

Yes, a few times over the years.

 

[Wibble]

Since 2017. I bought my first iX3M in 2017, and I upgraded it to the iX3M2 a few months ago.

Not familiar with those dive computers; what's the major updates between the two and does that improve your normal diving?

One thing with my 2017 Perdix is that it has not changed, software updates aside. It's still as usable, functional and reliable as it ever was.

I still have a Suunto D9tx which was a truly awful dive computer especially for decompression diving. Loads of issues: bricking itself at the drop of a hat (change from gauge to dive mode and wait 2 days); horrendous user interface with four buttons and long/short presses; ridiculous calculations (e.g. MOD of 28% = 1.4 / 0.28 = 5 or 40m/130ft, but in Suunto land it is 38m/125ft); insisting that changing to oxygen must be above 6m/20ft (i.e. breaking your ceiling to change to your deco gas); non-standard/proprietary algorithms (RGBM); deep stops(!); no software updates; incessant beeping...

Then there was the XDeep Black. A bottom timer that worked as long as a cheap Chinese torch. Thankfully not made any longer.

After buying the Perdix, life was so much better. A dive computer that worked and didn't need a 300 page manual to use. I like stuff that just works and especially like stuff that works well and is easy to use.

 

[NothingClever]

Halcyon's Symbios Blue just emerged. Same DC but without the wireless RB features.

https://media.halcyon.net/folder/Symbios-Blue-Handset-Computer.pdf

 

[Wibble]

Halcyon's Symbios Blue just emerged. Same DC but without the wireless RB features.

https://media.halcyon.net/folder/Symbios-Blue-Handset-Computer.pdf

Looks like an Etch-a-Sketch without the knobs!