Please explain (teach me)

[DwayneJ]

I would suggest spending some time with an instructor and going over dive planning and execution.

1. As a new diver, you need to understand how your computer is programmed (15ft vs 20ft) safety stops.

2. Your first dive of a multi dive day should be the deepest dive, not start shallow and dive deeper later.

3. Ascent should be 30ft/min or less... and most importantly this also includes the last 15ft to the surface... which should take 30 secs or more.

4. Be very aware of depth and the maximum you have planned for the dive. At 70'+ you really should have more gas for redundancy for you and your buddy.

5. Makes no sense (and bad for you) to head to the surface to complete a safety stop and/or deco stop then go back down again.

6. Dont do deco diving by accident or by design until you have had appropriate training in gas management and dive planning.

A well executed NDL dive may see you with 500lbs of gas at the surface or 1500lbs of gas at the surface - Do not bounce dive just to use up gas... because its bad for you.



Dwayne

 

[Thalassamania]

A few thoughts:

I would suggest spending some time with an instructor and going over dive planning and execution.

1. As a new diver, you need to understand how your computer is programmed (15ft vs 20ft) safety stops.

2. Your first dive of a multi dive day should be the deepest dive, not start shallow and dive deeper later.

As I understand it your computer may penalize you for doing so but it does not appear (despite our conventional wisdom) that mother nature is perfectly happy for you to make dives in whatever order you wish. It is not physiology that has problems with that, it is the models.

3. Ascent should be 30ft/min or less... and most importantly this also includes the last 15ft to the surface... which should take 30 secs or more.

4. Be very aware of depth and the maximum you have planned for the dive. At 70'+ you really should have more gas for redundancy for you and your buddy.

5. Makes no sense (and bad for you) to head to the surface to complete a safety stop and/or deco stop then go back down again.

In the case of a blown optional stop (OK, I'll try Pete's approach for a while) it makes not sense to return to the water since what the optional stop is there to do is lessen the risk of surfacing, something that you have already done. However, in the case of a blow mandatory stop, if you are not symptomatic, it is advisable to follow omitted decompression procedures, such as:

Should a diver not realize that they have exceeded the nodecompression limits prior to reaching the surface, or they have insufficient gas to perform in-water decompression, they should:

– Proceed to the surface at a normal rate of ascent

– Once on the surface they should notify the divemaster of their omitted decompression

– If asymptomatic, and the diver can be returned safely to the water within 5 minutes after surfacing, they should dive to the depth of the missed decompression stops and remain for 1½ times the required decompression stop time

– If the diver cannot be returned to the water within 5 minutes, they should be placed on oxygen for a minimum of 60 minutes

- If asymptomatic after breathing oxygen for 60 minutes, they should be observed for a minimum of 12 hours for signs and
symptoms of DCS and restricted from diving during this observational period

– If symptoms occur during or after breathing oxygen for 60 minutes, they should be transported (on oxygen) to the
nearest medical facility for treatment.
​

Note: If a diver is asymptomatic and unable to return to the water to complete omitted decompression, and a recompression chamber is available within 1 hour travel, the diver should be transported to the chamber for possible treatment using USN TT5 or 6.
​

6. Dont do deco diving by accident or by design until you have had appropriate training in gas management and dive planning.

A well executed NDL dive may see you with 500lbs of gas at the surface or 1500lbs of gas at the surface - Do not bounce dive just to use up gas.

Dwayne

A good warning, if just because repeated bounce diving can cause bubble pumping.

 

[rhwestfall]

Their use and how to avoid their abuse should be an integral part of every class.

Despite my own convictions about PDC's and new divers, I have no reason to object to that fabulous statement. I just wish that there would be a little more to the theory. Look at what has been typed in regard to the OP's question.... "Flots" nailed the explanation in a few paragraphs. How much more time would that take in a class?

Classes are "dumbed down" enough, lets see them brought back to what is needed.

I applaud the agencies/instructors that care about training the student. Many, IMHO, are just there for the $$.....

 

[DwayneJ]

A few thoughts:
As I understand it your computer may penalize you for doing so but it does not appear (despite our conventional wisdom) that mother nature is perfectly happy for you to make dives in whatever order you wish. It is not physiology that has problems with that, it is the models.

Thank you for the clarification - I had not seen that referenced elsewhere.

Dwayne

 

[fnfalman]

Does the manual set forth ascent rate guidelines and discuss the consequences of exceeding recommended ascent rates?

The manual stated that the ascent rate is set at 30-ft/s but no warnings or consequences about exceeding recommended ascent rate.

Various doctrines still call for 60-ft/min ascension rate.

 

[The Chairman]

Safety means "without risk" and by making a "safety stop" you do not eliminate all risk, you just lesson it.

Precisely why I don't like it. Its waffle speak.

 

[fnfalman]

Yes, in theory all stops are "deco" stops. However, some decos are necessary and some aren't. That's why the industry coined "safety stop".

Hell, the industry experts can't even agree on the benefits of deep stops.

 

[The Chairman]

– If the diver cannot be returned to the water within 5 minutes, they should be placed on oxygen for a minimum of 60 minutes

Oxygen is always a great option in this case. Too many boats and professionals freak out at the use of Oxygen, and it's not such a big deal. I had one charter suggest that if they use their O2 that they HAVE to initiate EMS. Such rubbish.

Asymptomatic is asymptomatic: without symptom.

 

[Thalassamania]

You got that one right. As Billy-Bob says, "green gas is good gas." Well ... he's right, up to a point.

 

[ben_wilson3301]

More like DOWN to a point.

Get it, a Nitrox joke, there aren't too many of those