trouble recovering bc from pool bottom

[boulderjohn]

I know you retracted your question, but a diver can suffer a lung overexpansion injury in 4 feet of water.

 

[Sleepdr]

Is an overexpansion injury likely in 10 foot of water?

Nevermind. I see that it is. Dumb question. I should know better.

That's not a dumb question at all. It shows just how counterintuitive it is to move into a foreign environment. We are conditioned as dirt-crawling air-breathing mammals to view the surface as safety. Snorkeling, you surface dive to 10 feet, then come back up with the same breath. It requires some additional thought to realize that taking a deep breath at 10 feet and holding it, so close to the "safe" surface, could be dangerous.

I'm still a pretty green diver, so will defer to the actual experts here. My GUE primer instructor had me working buoyancy & trim in 4 feet of water to take advantage of those physics. The pressure changes are so great near the surface that you are forced to be precise. In a simulated ascent from 15 feet, it was progressively more challenging to maintain precise stops at 8 feet and 4 feet.

 

[boulderjohn]

Some simple math using Boyle's Law [V(1) x P(1) = V(2) x P(2)] will tell you how much expansion there will be in a shallow pool. As Sleepdr indicated, the closer you are to the surface, the greater the expansion with a change of depth.

Let's look at what happens to a liter of air rising from 11 feet at sea level. 1 x 1.33 ATA = V(2) x 1 ATA. So the new volume at the surface will be 1.33--a 33% increase in volume. Altitude also makes a surprising difference. At our altitude in Colorado, ascending from that depth will cause a volume increase of the air in your lungs or BCD of about 40%.

 

[lindenbruce]

Oh quite contrar sir. Please do tell, unless it's not PG. Bruce

 

[Pullmyfinger]

My guess is about 9 out of 10 male students might find this statement humorous, motivating and/or fitting to the training; probably less for female students. So what makes it an appropriate statement to those students left out and uncomfortable by it?

I dive with females that would find that joke just as funny as I do.
Why do you imagine people would feel left out? You can usually tell by peoples body language and facial expression the spirit in which they mean something,
as I would imagine the students in the aforementioned class could.

Cheers,
Mitch

 

[Steve_C]

This exercise can also drive home why it is good to carry a spare mask.

 

[TMHeimer]

ladyfishfelt, You went back down and finished the job, despite a bit of panic. You should be commended. Based on what I recall from starting as a beginner, this would seem to be a difficult task when you maybe just learned how to take the unit on & off while seeing. An instructor I met in SC was giving me a few tips in the pool and had me do this (leave everything but weight belt, I think, on the bottom). I found it easy and actually fun. But I was getting help refining skills as a DM! The only thing I hated was the chlorine in the eyes. Then again, my vision now topside is close to 20-20, so I could in fact pretty much see what I was doing. Don't know how I would fare blinfolded (other than leaving all the stuff close to the side so you could feel your way to it, as suggested. You'd first have to feel your way to the second stage, of course, then you could relax having air and take all the time you need to get the rest on). As stated, drills like these have no real life purpose--they are just task-loading, but that's good.

 

[Sam Miller III]

Ditch and Recovery (D&R) (aka Doff and Donn in Eastern US) has been around almost since the beginning of civilian dive training

Diving to the bottom, removing the SCUBA unit, weight belt and the mask, returning to the surface for a breathe of air, diving down to the Scuba unit clearing the mouth piece, replacing the weight belt, replacing and clearing the mask and returning to the surface was introduced to the civilian diving world on page 58 of the 1955 edition of "Underwater Recreation," . Underwater Recreation, replaced the 1954 dive manual "Underwater safety" which first civilian manual published in July 1954 by the LA County program.

It was created as a training exercise to insure the basic diving student was comfortable in the water and was well prepared for any and all emergencies they may encounter in the harsh California diving environment. Often the LA Co UW Instructor would require the D&R to be repeated in the ocean prior to diver certification.

There are only three classifications of divers in the LA Co Program, Basic, which is probably equal to a supper duper popper diver in other programs, the three months long Advanced Divers program (ADP -the worlds first in 1966) which would equate to probably a Dive master and the famous or infamous four months long Underwater Instructors Certification course aka UICC. Each program required (requires?) D&R as a component of the training with increasingly greater depths.

In the instructors program a D@R is required in 33+ feet of open ocean, as well as free assents from 66 & 100 feet (Oh My! Oh My!)

There are two schools on instruction, one is train for nominal conditions and hope for the best out come, the other and to which I prescribe is train and retain for worst case conditions and be well prepared to handle worst case conditions.

I commend the NAUI instructor who is teaching this young lady..She will be well prepared and trained competent diver.

SDM

 

[ladyfishdvr]

I learned quite a bit from this exercise actually. How important it is to know what you are doing and to be prepared for anything.You have to be able to think on your feet or in this case fins. Scuba is a dangerous sport and you can die. This really scared me. Yes they tell you that but this really made that a reality for me. A bit of fear in what can be a dangerous sport is healthy. I did remember to breathe!! I need to slow down.

On Tuesday I will go back to the pool and do this exercise again until I get it right. I cannot hold my breath for 50 seconds while swimming or even walking. I am practicing and working on that. My surface dive skills need some work as well. I intend to do my check out dive in the quarry in May and I need to be ready for it. I have gotten a lot of really good advice, which I intend to use. And yes I think I will pick up a spare mask as well.

 

[Sam Miller III]

ladyfishfelt,

Don't worry...You will do just fine! There are many many others who have faced the apprehension you are experiencing.

You have a great instructor who is teaching you diving the way it should be taught. When you finish the course you will be a diver rather than one who dives.

Do to timing, education and geographical location I have been a consultant to four diving companies. I recall a meeting many years ago with the late Harry Rescigno, the founder of Sea tec/Inflatable systems about a new inflation unit. I had proposed a number of changes to a product. Harry responded "I am making this inflation unit for the masses of people who dive, not for divers-- and there is a difference"

I suspect with your training you will be come a diver rather than one who dives..

SDM