Uncontrolled ascent

[ScubaFreak]

i dive year round in a dry suit and have no issues, however, it is always wise to be careful with your positioning when wearing a dry suit, and obtain dry suit certification. I've heard many horror stories of people who just buy a dry suit with no certification, and assume things are the same, but dry.

At our LDS, a drysuit can't be bought without certification, and normally, we will offer a dry suit course at a substantial discount.
One thing that I do, along with many others, but has seen some disagreement on this board in the past, is the use of ankle weights with a drysuit.

I would never dive in a drysuit without ankle weights. Never.
I find it's easier to maintain a horizontal position, as your legs don't constantly rise behind you. I also find it easier to somersault out of an inverted position with ankle weights on. But JBD is right, there are no ankle seals in drysuits, but one thing i have read somewhere is an ankle dump, which I think is a fantastic idea.

SF

 

[MXGratefulDiver]

I've just started to get my OW cert, so forgive me if this is a dumb question. Since I'll be diving in 50 degree water, I opted for the additional training (an extra pool session) and will be doing my OW dives in a dry suit. Reading this post, and having heard a few stories from other divers, it's frankly got me a little anxious about using a dry suit.

I encourage the questions ... in scuba diving, it's what you don't know can get you into trouble.

So I'm curious, if you were in an uncontrolled feet first ascent, is it impossible to bend over and break the seal around the ankles?

Normally you won't have ankle seals ... only rental drysuits come with those, since they have to accommodate people with different size feet. When you purchase your own suit, it will either come with boots or neoprene "socks".

In any case, it's easier to access a wrist or neck seal ... if that becomes a "last option". Keep in mind that breaking a seal will immediately flood your suit. You always want to try other options first.

Also, would you ever consider unzipping the dry suit and flooding it in a situation like this? Or would that just add even more problems to bad situation.

Never really considered it ... it's often not an option as your zipper will be under your BCD.

Last, how easily can someone get into a situation like this! Is it normally avoidable as long as you don't panic.

It's not hard to get into an uncontrolled situation if you are not paying attention ... it's easily avoidable if you do. I will say the most common occurances of runaway ascent in a drysuit happen when the diver is new to using the suit ... which is why you should stay relatively shallow for those first dozen or so dives.

Most problems related to scuba can be remediated by keeping a clear head and thinking through what you have to do. That's why every agency has a mantra ... stop, think, act ... or a similar variant. The idea is that a scuba diver's best friend is a clear head and a calm demeanor.

... Bob (Grateful Diver)

 

[MXGratefulDiver]

I would never dive in a drysuit without ankle weights. Never.
I find it's easier to maintain a horizontal position, as your legs don't constantly rise behind you. I also find it easier to somersault out of an inverted position with ankle weights on.

I'm not a big fan or ankle weights ... primarily because they usually tend to mask a symptom rather than fix the problem. The main problem being that the ankle weights are used to offset the fact that the diver has more air in the suit than really needed, and is using the ankle weights to counteract the buoyancy shifts produced by all that air.

An alternative would be fin-keepers, which are little Y shaped rubber bands that go around your foot to prevent expansion of the boots when air enters. The advantage to fin-keepers is that they prevent the air from getting into the boots in the first place, which makes it easier to invert when wanting to look under a ledge or something.

But JBD is right, there are no ankle seals in drysuits, but one thing i have read somewhere is an ankle dump, which I think is a fantastic idea.

Apollo makes a nice, relatively inexpensive neoprene suit with ankle vents. Some people love them, others hate them. In practice, the problem is that they are not adjustable and often vent air when you don't want them to. This is especially problematic for people who use their drysuit for buoyancy control.

... Bob (Grateful Diver)

 

[vjongene]

:06:
I should preface this by saying I don't (generally) do deco diving (and was never trained in it) and don't know CMAS procedures.....(so this is more of a question from me for my own understanding)

.....but I was under the impression that if you'd had an uncontrolled ascent from depth and broke all your deco stops, you were at extremely high risk of DCS (even if no immediate symptoms visible), but if I am reading the above correctly it states the CMAS procedure is to go back down to de-gas ??

I thought the usual procedure would be to get to O2 and not go back down (as you'd run the risk of the DCS happpening when you were underwater which makes you difficult to rescue)?
..or am I misreading the above (or incorrect in my assumption)

...from the post, the guy didn't go back down and was immediately put on O2 [but had been given the option of another tank]

I just checked my course materials to make sure I had this right. The procedures we learned are as follows:

1) The ascent speed was too fast, but buoyancy control regained: stop at whatever depth you were when regaining control, and stay as long as it would have taken to get there at a safe speed. Resume scheduled deco stops.

2) One of the deco stops was blown, and the diver popped to the surface: return to the deco stop before the one that was blown, repeat that stop, and then add 50% to all others.

3) Uncontrolled ascent (i.e. the situation described here): do not stay at the surface more than 2 min; return to a depth of half the max depth reached during the dive, and stay there for 5 min; ascend at prudent speed, and calculate the deco stops using a bottom time corresponding to the entire elapsed time until the end of the 5 min at half depth.

I know that thiese are not the procedures taught by other agencies, and as Lamont said there is a risk associated with a stressed diver returning under water. Many advocate immediate O2 and a chamber ride as a safer alternative. IMHO it depends on how the diver is feeling. I once popped to the surface from 20 m while I was learning to use a dry suit, and after fixing the problem (a slipped boot and fin) I just returned under water and did an extended safety stop at 5 m.

BTW, returning to depth (or half depth) will re-compress any forming bubbles, and DCS should not manifest itself until the diver returns to the surface. The risk of DCS at depth is much less than on the surface. The real risk is that the diver may panic and make the problem worse (e.g. by swallowing water and drowning).

 

[DA Aquamaster]

The "skipped deco stop" procedures are based on analogy to what divers with shipboard chambers will do routinely, which is to surface immediately skipping all their deco, climb into a chamber and repressurize and complete deco obligations. That's similar to blowing off deco, surfacing, grabbing a tank and heading back down. In-water recompression is riskier though because you're not a chamber and you can drown if something bad happens.

For rec divers the recommendation is not to attempt in-water recompression for a case of DCS or rapid ascents / skipped safety stop, but the deco obligation of a rec diver is minimal and therefore DCS symptoms will probably be minimal and will likely be treatable with 100% O2. The hazards of IWR tend to outweigh the risks of DCS for recreational divers. For tech divers, it seems like opinions differ widely on IWR from being insane to being proper procedure...

Being at least 5 hours away from the nearest recompression chamber on an average deep deco diving day, I am inclined to at least consider in water recompression as a means to perhaps prevent the onset of DCS symptoms should the need ever arise.

With ship board decompression the diver normally completes the deco stops to the 40 ft mark and then is pulled to the surface, stuffed in a chamber and blown down to 50' in a total of 2-3 minutes. While in the chamber at 50', the diver will be using a mask with 100% O2 - a very extreme O2 exposure and not something any sane diver would consider doing underwater. In water recompression is similar, but only remotely so as there are significant differences in the PO2 encountered during the deco.

I think it's important to distinguish between descending to complete a missed deco procedure, which is probably a reasonable procedure, versus doing in water decompression as a treatment for a diver who is already symptomatic before they decend, which in all but the most remote and isolated situations is probably a really bad idea.

All missed eco procedures that I am familiar with require a very short surface interval and that the diver be asymptomatic. Treating a symptomatic diver with in water recompression would at a minimum require surface supplied gasses, a full face mask, an in water saftey diver, a stage of some sort, and warm enough water and/or adequate thermal protection to keep the diver warm throughout what amounts to a very long procedure.

 

[lamont]

I think it's important to distinguish between descending to complete a missed deco procedure, which is probably a reasonable procedure, versus doing in water decompression as a treatment for a diver who is already symptomatic before they decend, which in all but the most remote and isolated situations is probably a really bad idea.

Yeah, you're absolutely right, I don't think I was being careful in distinguishing between IWR and missed deco stop, and there is an important difference there.