Decompression Stop Guidelines - What we have to do if got deco alert?

[The Chairman]

Adding a safety stop when you're drifting with no knowledge of where your boat is and are cold (not necessarily an uncommon scenario in some areas) might not be the safest thing to do.

Why would anyone do this? I'm certainly not suggesting it.

If you're drifting, you should have a flag. If you lose the flag, you should shoot an SMB immediately so the boat(s) know where you are.

There are a few reasons to abort a safety or optional stop.

• Short on air (Never experienced this)
• Physical threat
  • Moon jelly invasion!
  • Two aggressive bulls circling
• Injury
• Cold (Never experienced this)
• Discomfort
• Buddy has an issue (See above)

There are also reasons to extend your safety stop

• Cool critters!!!
• Came close to your NDL
• Crowded on the ladder
  • Why wait on the surface?
  • Especially if it's rough???
• Need to chill or rest
• Feel like it
• Did I mention some of the cool critters I've seen on my safety stops?
  • First Whale Shark seen
  • Feeding Sail fish! Still vivid in my mind!
  • Porpoise
  • Sea Lions

Unfortunately, the two most common reasons that divers miss their stop are ignorance and apathy.

 

[dmaziuk]

Adding a safety stop when you're drifting with no knowledge of where your boat is and are cold (not necessarily an uncommon scenario in some areas) might not be the safest thing to do.

Maybe, but in that scenario, is drifting with your head out of the water and cooling down from evaporation (while the rest of you is still immersed and no less cold than before), any better than drifting at SS depth with the SMB out? Obviously, if you're certain they're not looking for your SMB and you must start flashing lights and blowing sirens etc. now!.. but then you're looking at 2 more wrongs. Both potentially avoidable.

 

[Patoux01]

4 (or 6) minutes can make you drift a long, long way.

 

[boulderjohn]

4 (or 6) minutes can make you drift a long, long way.

I am going to need some help on this. I am not sure what the point is.

Is the point that if you do a drifting safety stop/decompression stop while a boat doesn't know where you are, then the boat will have trouble finding you? That is certainly a possibility, and that is one of the most important reasons that anyone who has any chance of getting into that situation should have a DSMB and be ready to deploy it any time they may have to do a drifting ascent.

This is an extremely common scenario in open ocean decompression diving. If you are on the boat while this is happening, you see the crew looking out at safety sausages bobbing along on the top of the ocean, waiting to see the heads pop up next to them so they can pick up the divers.

 

[dmaziuk]

4 (or 6) minutes can make you drift a long, long way.

If the current is dragging you into open ocean and nobody's looking for you, you better have a PLB and a Nautilus. I'm not sure how much difference activating them 5 minutes later will make to the Coast Guard search effort.

 

[lermontov]

@The Chairman

Your comments are valid however my question was why is riding the NDL more aggressive that accruing 5 minutes of deco, I ran both scenarios through subsurface and was interested to see the difference in the heat maps however I cant see any discernible differance -if anything the 5 min of deco showed higher off gassing rates. Im sure you could fudge the times either way but I wouldn't classify this as conclusive that riding NDL is much more aggressive-
Maybe someone with more expertise can explain?

 

[The Chairman]

Your comments are valid however my question was why is riding the NDL more aggressive that accruing 5 minutes of deco,

It's a matter of comfort for me. I'm not asking anyone else to dive the way I dive. Whenever I use a meter, I want my readings to be somewhere in the middle of the scale. When you get to the edges, your accuracy falls off and it can be quite dramatic. So, trusting an algorythm at the edge of it's NDL is a bit disconcerting to me. It's not that I haven't done it, but I don't make a habit of it and I will stay longer at my safety stop. Hell, I pad my deco stops and will wait a few minutes at the surface it I can before I get out. That's what I like about cave diving: no one sets my schedule but me. I can take as long as I want or need on any aspect of my diving.

 

[Tom_Ivan]

Secondly, do you understand the situations when it WON'T clear on ascent, or may even continue to rise?

I don't. What situation would would cause your deco obligation continue to increase as you ascend?

 

[gfaith]

@Tom_Ivan

Andy may be getting up and want to talk with you about your question. In the mean time..
Here is a good write-up he wrote.

Best Ascent Speed for Scuba Diving

I think it will clear up some of your questions.

 

[TrimixToo]

Very well put.

Nobody suggests you should.

Contingency planning involves reasonably predictable and foreseeable issues that could arise.

Technical diving courses introduce many of these foreseeable problems.

Experience, prudence, foresight and local diving knowledge will introduce more.

The danger is when people dive in ignorance of risks and consequences. Recreational diving courses typically gloss over these (at best), or absolutely deny them (at worst). Very, very few recreational instructors are actively enlightening divers on risks and consequences.

Jumping into technical (deco, overhead etc) diving, without the change of educational tone that tech-level training enables, can allow recreational divers to persist in a rose-tinted, risk-blind, outlook that can lead them into very unforgiving situations.... where most failures are beyond their capacity to resolve and the consequences are more damaging than they would predict.

This is why technical (all?) divers should progress the scope and challenge of their diving slowly and keep their dives forgiving / survivable until they've had chance to learn the lessons and broaden their experience.

Recreational no-stop diving is inherently safe and forgiving of failures. It's the place to make your mistakes, get away with it, and learn lessons.

Each step above that... into deco, into accelerated deco, into extended range, into mixed gas, into hypoxic gas, to expedition level tech depths.... becomes significantly less forgiving and offers more severe consequences to any failure and not having a practicable contingency measure for any issue that might arise.

Even where divers might be 'risk-educated'... there can also exist situations where those known risks are perceived only as hypothetical. Thereby enabling a "it can't happen to me" mindset. That mindset can be just as bad as being risk-ignorant.

When experience really is at a suitable level, the diver will have no false illusions of the risks they face, the consequences of failing to mitigate those risks with adequate contingencies... and the fact that those risks really do apply to them.