sudden uncontrolled ascent!

[Codyjp]

I figured that but I thought there might be a slight chance it was possible. I guess the question should have been "what did you look like when you got to the surface...

Humor me guys!

 

[Ayisha]

Did you POP out of the water on the surface like a polaris missile? You always here of this analogy but there isn't any proof that it could actually happen, you might be the one to decide this urban myth for us.

It has happened. There was an accident last summer (June '08) on the Jodrey in Brockville Ontario where a diver was seen popping up to his waist area. Witnesses believed he was already deceased at that point or shortly thereafter. There was a thread on the accident here last summer. I was diving with the charter op that weekend, but was not on that boat. According to a reliable witness, a polaris type ascent was written into the police report.

If that happens, you will more than likely succumb to your injuries, so let's all be careful down there.

 

[LeadTurn_SD]

The best thing this diver did was go back down to recompress and then decompress properly. Divers have died who have had uncontrolled ascents to the surface and then stayed at the surface.

If you have a similar incident, go back down within 3-5 minutes or less - that's a safe time window before bad things can start happening. Then do a several stops at depth and along one at 20 feet. As this examples shows, going down immediately is better than staying at he surface. I know this is controversial, but the statistics, including this case, show immediate in water recompression is the best course of action in these types of cases. If there is a long surface delay and symptoms start setting in, then that's a different kettle of fish.

I see two problems with this.

As I understand the problem:

1.) An uncontrolled ascent to the surface, followed by immediate return to depth risks "bubble pumping". The risk is that a fast ascent can cause rapid offgassing, and some "bubbling", but hopefully the bubbling is on the venous side and will pass "safely" out through the lungs if you remain on the surface.... but if you immediately descend the risk/theory is that the bubbles will recompress and pass to the arterial side, where they may become lodged... not good.

2.) If the rapid ascent has in fact resulted in a frank DCS hit, it is highly controversial and generally not recommended to attempt in-water recompression. There are longs threads about this, but in general my understanding of the current "best practice" in a recreational setting is to have a diver who is displaying DCS symptoms remain at the surface and go on O2.

My feeling is that an uncontrolled ascent from depth should be a "dive ender" for the day.

Others more knowledgeable than I can correct this if they have different current info.

Best wises.

 

[*dave*]

If that happens, you will more than likely succumb to your injuries, so let's all be careful down there.

If the ascent is botched, I'd agree. But, many people have made many ascents from 60'+ at ascent rates in excess of 120fpm without any apparent effects. The primary danger is over expansion and that can be managed. Secondary risk is DCS and that would take some time after ascent to present itself if the dive is conducted within NDLs.

 

[Blackwood]

It has happened. There was an accident last summer (June '08) on the Jodrey in Brockville Ontario where a diver was seen popping up to his waist area. Witnesses believed he was already deceased at that point or shortly thereafter. There was a thread on the accident here last summer. I was diving with the charter op that weekend, but was not on that boat. According to a reliable witness, a polaris type ascent was written into the police report.

If that happens, you will more than likely succumb to your injuries, so let's all be careful down there.

My physics sense is tingling. I don't buy it, regardless of what witnesses reported.

If I fill a wing or BCD at depth and let it go I bet it won't jump out of the water even without the weight of a diver attached to it. There is a fundamental difference between a missile and a buoy.

In fact, next time I'm on a boat I'm going to suggest we do just that, and film it for posterity.

 

[pdelannoy]

With the Ladyhawk, you need to learn to make yourself upright to vent air by raising your shoulders.

 

[sabbath999]

My physics sense is tingling. I don't buy it, regardless of what witnesses reported.

If I fill a wing or BCD at depth and let it go I bet it won't jump out of the water even without the weight of a diver attached to it. There is a fundamental difference between a missile and a buoy.

In fact, next time I'm on a boat I'm going to suggest we do just that, and film it for posterity.

Please make sure to post that, you now have me curious

 

[String]

In fact, next time I'm on a boat I'm going to suggest we do just that, and film it for posterity.

There is the method to test it consisting of taking a breath at the surface, wearing loads of lead, going down to 7m rapidly by dumping the wing then at the bottom fully inflating the wing (dual bladder even better) while at same time dumping that weight.

And yes its really really hard (likely impossible) to breach entirely. Best ive seen is up to the waist. The sheer drag of water prevents enough inertia or speed from being gained to do any more.

Oh yeah and for me, missed deco means im going back down to try to clear it and NOT staying sat on the boat just waiting for the bend to happen.

 

[mbwilliamn]

I reckon I have buoyancy issues. I am skinny (120 punds), I use 12 punds with aluminum tanks and 8 punds with steel tanks. Usually I am pretty good at controlling it but now I dont know what to think. I was using 12 punds integrated weights that day with my aluminum nitrox tank.
Thanks for your expert advice!

Looks like you are significantly over weighted. With an Al tank and a 3 mil you should use about 4-6 lbs (w/ a skin maybe 2-4). This overweight creates a large airpocket in your BC that changes your buoyancy state significantly with a change in depth.

When you get to depth, STOP and establish your neutral buoyancy. If you do this, you should not have to touch your inflator again until you have used at least 500psi (~1lb of neg bouyancy), or change depth more than 5 or 10 feet (assuming you are at about 60 ft).

Your first response to a slight change in depth should be your breathing....if sinking take a full breath (DONT hold it), if ascending exhale completely. Remember your breathing is your fine buoyancy control, but it takes a second to act. If you exhale completely, your body will slowly stop going up and then start to sink. Just as you start to sink, slowly begin your inhale. You will likely get a full breath and still be sinking (though your rate will be slowing). As you start to slowly exhale you will stop sinking an slowly begin rising. Practice this and you will perfect your control.

Dumping air - If using the button you MUST get your hand completely above your BC and have the hose extended. I teach pulling the dump valve on the shoulder or pulling the inflator to use the build in dump valve. It allows quick action without changing your position in the water.

 

[mbwilliamn]

...the diver was trying to dump air out of his bcd but instead was hitting the inflator and kind of took a ride up...

...but I think gbray's exactly right in the fact that it does take 40 or 50 dives to start to become decent at buoyancy...

This is the main reason I don't teach the deflator button to dump air. Simple, button = up, Pull (dump value)= down

I disagree with the number of dives to develop buoyancy control....maybe to make it second nature. The keys are: Get them weighted right and; Take that magic elevator button away from them. If they stop pushing the buttons, they'll start using their breathing to control their buoyancy. Then its practice, practice etc, from the first pool dive.