AOW Navigation OOA

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Npallasi

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Location
Singapore
# of dives
25 - 49
During my navigation dive in my AOW course, I very nearly ran totally, completely out of air.

The dive was separated into 3 parts:
1) Descend a few meters. Count fin cycles needed to complete 25m. We were diving off a boat 25m long.
2) Descend all the way to the bottom. Navigation in a straight line, with buddy on the compass and I counting fin cycles, and returning. Then it was me on the compass and buddy was counting fin cycles, to and fro. Distance covered: 25 m x 4.
3) Navigation in a square. Buddy was guiding by compass first, and I was counting fin cycles again. After the square was completed, we switched roles. Distance covered: 25 m x 8.

Upon finishing the exercise, I looked down at my gauges, and realised the air pressure needle was on zero bar (usually we ascend on 50 bar). I performed CESA, and fortunately there were still a few good breaths I could take from the tank. My instructor and buddy followed me up. On the surface, when I asked my buddy what his gauge read, he was on zero too.

I think this is what happened.
1) We were finning hard when we were doing our navigation exercise. I had to fin hard to keep up with my buddy, who was faster than I was. We were over-exerting ourselves underwater.
2) We were too focused on finning and our compass, we forgot to check our gauges often.

I suggest that students be told that the navigation exercise is not a race, to avoid over-exertion and to check gauges often.

EDIT: I must state that I was falling a little behind my buddy and instructor when I looked at my gauge and decided it was time to perform CESA. I didn't have any tool to sound a signal. When my instructor looked back (and up) for me, I gave him the OOA signal and continued up.
 
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Firstly, you handled the emergency well. You decided that you needed to surface immediately, made contact with your buddy and instructor and ascended.

However, having already completed OW, you should know to frequently check your gauges. I check my gauge every 10 or so minutes to ensure it's dropping at a slow and steady rate, which is also an indication I'm not over-exerting and there are no leaks from my first stage that I am unaware of.

You made a mistake which could have ended in disaster, but you are able to diagnose what went wrong and how to prevent it from happening again so good on you.

And diving is never a race :wink:


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I'd say your assessment of what happened is the most likely. As an instructor myself I often find that students run lower on Navigation dives than on others. I put it down to a combination of the following:

1) When focusing intently on any new skill for the first time (compass work, dive leading, photography etc), breathing in general and any breathing techniques usually employed by the diver tend to go out of the window.

2) When focused on compass and nav tasks pretty much every diver in training will tend to fin/swim much faster than their usual rate just to get it done.

In predive briefings for Nav dives I usually make a point of mentioning both of these facts to my students, party so they are aware of their air consumption and do regular air checks, but also as a reminder to swim at regular speed - the whole point of counting kick cycles and using a timing device to measure distance is completely pointless if your measurements are based on double speed!

Sounds like you kept a cool head and followed the correct procedures though, which is a testiment to your training. And on the up side, although it may not have been the ideal training dive, you definitely learnt something!

I'm guessing you were on a PADI course? So on a side note if you want to be 100% true to the training standards, you should have done 30m, not 25m. Saying that, as long as students learn something about their kick cycles and distance measurement for their own style (and speed!), the actual distance used doesn't make a huge amount of difference IMOH.
 
Did you start at 200 bar? How deep was the bottom?
 
When previously taught skills (such as situational awareness... gas monitoring) degrade when new skills or demands are added (increasing task loading), it indicates that the previously learned skills have not been reliably embedded by the diver as instinctive, automatic processes.

This can happen at any level of diving, and indicates that further time and effort are required to reinforce and ingrain known skills, before moving on to learn new stuff.

Don't under-estimate the importance of ingraining core scuba skills (those taught at OW level) - they will shape your progress however advanced your diving becomes. They are the foundations of your diving, but also often the most neglected by divers, eager to advance.
 
Thank you for sharing your story. It's not easy to share stories that do not show us in the best light, but it can really be helpful for others who read these posts so they can learn from our mistakes.

During my navigation dive in my AOW course, I very nearly ran totally, completely out of air.

The dive was separated into 3 parts:
1) Descend a few meters. Count fin cycles needed to complete 25m. We were diving off a boat 25m long.
2) Descend all the way to the bottom. Navigation in a straight line, with buddy on the compass and I counting fin cycles, and returning. Then it was me on the compass and buddy was counting fin cycles, to and fro. Distance covered: 25 m x 4.
3) Navigation in a square. Buddy was guiding by compass first, and I was counting fin cycles again. After the square was completed, we switched roles. Distance covered: 25 m x 8.

Upon finishing the exercise, I looked down at my gauges, and realised the air pressure needle was on zero bar (usually we ascend on 50 bar). I performed CESA, and fortunately there were still a few good breaths I could take from the tank. My instructor and buddy followed me up. On the surface, when I asked my buddy what his gauge read, he was on zero too.

I think this is what happened.
1) We were finning hard when we were doing our navigation exercise. I had to fin hard to keep up with my buddy, who was faster than I was. We were over-exerting ourselves underwater.
2) We were too focused on finning and our compass, we forgot to check our gauges often.

I suggest that students be told that the navigation exercise is not a race, to avoid over-exertion and to check gauges often.

EDIT: I must state that I was falling a little behind my buddy and instructor when I looked at my gauge and decided it was time to perform CESA. I didn't have any tool to sound a signal. When my instructor looked back (and up) for me, I gave him the OOA signal and continued up.
 
I have never been OOA, BUT when I took the nav course, it was in a big quarry. There were two of us. I was to swim a fairly long route out with several way points. Then the other person was to navigate back. I got to thinking that this was a long way to go on an AL80 and let myself get rushed*. We dropped and I took off and while swimming took my first heading*. There is an old road bed and when I reached it I convinced my self I was on the north side rather than the south side (no I did not check my compass)*. Charging along* I finally stopped and burst out laughing when I saw an object that I knew was on the far side of the quarry from where I wanted to be.

Multiple lessons learned as indicated by the *. But again the cause was obsession with a task and being in a hurry.

One of the first lessons of Navigation is to know where you are starting from. Important in NC diving where you need to get back to an anchor line on a ledge or a broken up wreck.
 
I have never been OOA, BUT when I took the nav course, it was in a big quarry. There were two of us. I was to swim a fairly long route out with several way points. Then the other person was to navigate back. I got to thinking that this was a long way to go on an AL80 and let myself get rushed*. We dropped and I took off and while swimming took my first heading*. There is an old road bed and when I reached it I convinced my self I was on the north side rather than the south side (no I did not check my compass)*. Charging along* I finally stopped and burst out laughing when I saw an object that I knew was on the far side of the quarry from where I wanted to be.

Multiple lessons learned as indicated by the *. But again the cause was obsession with a task and being in a hurry.

One of the first lessons of Navigation is to know where you are starting from. Important in NC diving where you need to get back to an anchor line on a ledge or a broken up wreck.

Long ago I was told that you can go further on a tank by swimming slowly. Tested it in a shallow quarry (15'-25') making my first 1:15 dive swimming a zig zag course through most of the many sunken objects (planes, school bus, cars, motorcycles, etc). Had I been swimming at my (previous) normal speed, I'd only have reached half as many objects in about 0:45.

Now I always tell students "To get further, swim slower."

Of course current or a DPV changes the equation and as always YMMV.
 
Did you start at 200 bar? How deep was the bottom?

I started at 200 bar. I don't recall the depth immediately, but it was definitely less than 20m. During my AOW, we only exceeded 20m for 2 dives, the deep dive and the leisure dive after the 5 adventure dives.

When previously taught skills (such as situational awareness... gas monitoring) degrade when new skills or demands are added (increasing task loading), it indicates that the previously learned skills have not been reliably embedded by the diver as instinctive, automatic processes.

Yes, this is true. After that incident, I learned to check my gauges often and let my instructor know when I was close to "low on air".
 
I think you did well with the circumstance you found yourself in. Did you pass the course? Did the instructor ask to repeat that particular dive?
 
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