hand signals from diver to boat (in clear water)

[ballastbelly]

hello again, i was trying out a diving simulator on my pc to learn more about my dive computer (zoop),
and was quite surprised to see how much bottom time was reduced when touching 30m. May i ask what usually happens in for these 3 questions please?

I simulated a botched up dive where i ended up having to do a deco stop. the zoop offered me to spend 10min deco anywhere from 5.9 to 3m. i spent them all at the ceiling, as i reasoned that at the floor i would be consuming air at higher pressure, air would last less & i would actually be absorbing some new nitrogen from the air breathed in at 5.9m. would you have choose floor or ceiling?

How long will 50bar last at the safety stop, given the anxiety of a real deco situation?

In clear visibility is there a hand signal when at 3m to wave to the boat so they can lower another tank&reg? if they dont get it,& you ran out of air would you swim up to the boat, yell for another tank & go back down quickly to 3 m (or deeper?) to finish the deco?

thanks
B

 

[Mike.D]

Technical divers carry 2 dsmb's. a standard red or orange to tell the boat where they are or to hang onto during deco obligations they may have, and a yellow 'help needed' which is (as discussed prior to the dive with the crew) a signal to send down a diver with air as there is an emergency.
I don't know your current level of training however advanced nitrox/deco courses teach a lot about this. And yes at 30m your at 4ata so your bottom time (on air) will be significantly reduced. That's basic dive theory.



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[KeithG]

I think you are over thinking things a bit. Instead of worrying how to get out of trouble, you should concentrate more on making sure you do not get into trouble.

I suggest you get some experience, understand and practice the "rules" for your current level of training. Once you have gained some level of competence, seek additional education and training for more advanced dives.

As an experienced recreational diver I have never worried about your hypothetical situation as it will never happen to me. Following my training will prevent getting any where close to having deco situations.

 

[Mike.D]

Giffenk, you are right about not getting yourself into trouble, however it doesn't hurt to have in idea of what to do should you get yourself into it.
Following your training will reduce the risk of getting yourself into any deco situation, but will not be able to 100% prevent it unless your diving in 10m of water, no-overhead with a small tank.
Ballastbelly did say he was looking to start tech, wreck dives so I believe he should be made aware of the emergency actions to put in place instead of being ignorant and simply believing it was completely avoidable on such dives.


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[kr2y5]

Most people do safety stops in-between, at around 15 feet. Being very close to 10 feet carries a bit more risk of exceeding the ceiling if your buoyancy is not dialed-in, or weighting not right, and the Zoop will penalize you for exceeding the ceiling, even if very briefly. In addition, if you are not careful, you might ascend, it can be harder to control buoyancy closer to the surface. You are not going to be on-gassing at 20 feet in any imaginable scenario, and if you are not experienced, closer to 20 feet is probably safer for you. On the other hand, if you try to hover at exactly about 20 feet, Zoop will stop counting every time you dip below 20 feet, which can be really annoying, so 15 feet (4.5m) is a good compromise. In practice, the exact depth you hold will much more likely depend on who else is doing the stop and competing for the real estate on the anchor line.

At the stop depth, those 50 bar should generally easily last you for 10-20 minutes, depending on your air consumption, anxiety level, and the type of the tank. For starters, you can assume 1 cuft of air per minute of the base surface consumption if anxious, add 50% to account for the increased density at 15 feet of depth as compared to the surface, and multiply by the time at the stop, e.g., 15 cuft of air consumed over 10 minutes. 15 cuft is about 20% of the capacity of an AL80. If the tank is full at 200bar, that means you will consume 40bar over 10 minutes. In reality, in calm conditions, your consumption will likely be closer to half of that. And, the time about twice longer. Or, it could be twice shorter if your buddy unexpectedly runs OOA, and needs to share gas with you...

To signal the boat, as someone mentioned, you could deploy an SMB, and I would only add that you can attach a slate at the top with a message if necessary. Carrying an SMB is always a good idea when boat diving, and deploying it from a safety stop is an important skill, often taught in AOW.

 

[KeithG]

Giffenk, you are right about not getting yourself into trouble, however it doesn't hurt to have in idea of what to do should you get yourself into it.
Following your training will reduce the risk of getting yourself into any deco situation, but will not be able to 100% prevent it unless your diving in 10m of water, no-overhead with a small tank.
Ballastbelly did say he was looking to start tech, wreck dives so I believe he should be made aware of the emergency actions to put in place instead of being ignorant and simply believing it was completely avoidable on such dives.


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Agreed. And the best way to find out how to handle this type of situation is to get the proper training.
asking random questions from a bunch of strangers is a very poor second choice. Getting only half of the required knowledge is even worse.

Following my training will 100% guarantee prevention of deco obligation. If I incur a deco obligation it means I made a mistake and did not follow my training.

 

[Mike.D]

Agreed. And the best way to find out how to handle this type of situation is to get the proper training.
asking random questions from a bunch of strangers is a very poor second choice. Getting only half of the required knowledge is even worse.

Following my training will 100% guarantee prevention of deco obligation. If I incur a deco obligation it means I made a mistake and did not follow my training.

I do agree with you, but again following your training WILL NOT 100% guarantee prevention of an emergency, leading to a deco obligation. Following your training will help prevent it, but cannot and will not guarantee absolute immunity from a diving emergency, whether to you or another diver, leading to deco.


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[beanojones]

Following your training will reduce the risk of getting yourself into any deco situation, but will not be able to 100% prevent it unless your diving in 10m of water, no-overhead with a small tank.
Ballastbelly did say he was looking to start tech, wreck dives so I believe he should be made aware of the emergency actions to put in place instead of being ignorant and simply believing it was completely avoidable on such dives.

I can 100% guarantee that I will never go into deco unintentionally. Everyone can. I cannot gurantee never getting bent, but that's a different matter, because people get bent on 20 minute dives to 30 feet.

I agree that the theory is worth pursuing, but i strongly agree with Giffenk that there is simply no reason to ever go into deco accidentally any more than there is any reason to run out of air accidentally. Since both situations are equally life threatening, there is simply no excuse to end up in deco unintentionally. Someone who does so should be thinking about whether they should be diving since they are having a major "between the ears gear" failure. Overhead diving is for technical divers only for a reason, and a deco obligation is an overhead environment.

At least with running OOA, there can be gear failures that cause problems beyond a diver's control. Going into deco unintentionally is simply inexcusable. There is a reason why boat operators check computers and kick divers off boats for going into deco on recreational dives. People who get sloppy with their actions tend to spread danger.

They are the accomplished bad diver:
http://www.johnchatterton.com/2013/03/19/accomplished-bad-divers/

That article should be required reading for anyone thinking deco withOUT tech training is OK. From a preofessional's viewpoint, it simply endangers the industry as a whole.

---------- Post added July 4th, 2014 at 02:38 AM ----------

following your training WILL NOT 100% guarantee prevention of an emergency, leading to a deco obligation.

Yes it will. 100% and without reservation. There is no recreational situation in the world that can force you into unintentional deco.

There are lots of stupid things people do, like going into overhead environments, but that is not recreational diving, it's tech diving without training.

 

[Mike.D]

We are not talking about intentionally or unintentionally going into deco. Just the fact that it can happen for whatever reason and if it were to happen what would you do.
Also, an overhead dive does not automatically make it a deco dive, although it does introduce some new hazards to be aware of.


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[Mikko Ilari Laakkonen]

But deco dive is automatically an overhead dive. One simply does not go to deco by accident .