Solo Diving Checklist? Musts?

[Slamfire]

Thanks for the reply, Akimbo. A few months ago I attended a lecture delivered Kirk and Mandy-Rae (Cruickshank) Krack of Performance Free Diving. It does sound very attractive to have the free diving skills to do free ascents from say 180'. My hesitation in relying too much in freediving is because I have already been injured doing breath hold swims. I was about 13 years old show boating my capability to do underwater laps at the pool. I pushed myself too hard and damaged the inner ear equilibrium center. I took a couple of weeks (months?) to recover. Since then, I've never pushed myself beyond too hard when it comes to doing breatholding swims. I just don't want to get injured again.

I've comfortably done free dives to 45' stayed at the bottom for a few secs and gone up again. More recently in 2009, I did get measured horizontally breathhold swimming 65 feet at a depth of 25' with my doubles on my back. Again, I didn't feel like I was pushing myself. Doing a free ascent from 130' at a max speed of 60' per min equals 2 mins of breathholding. It's not an extraordinaire amount of time, given that you're hyperoxygenated, not swimming and mostly exhaling. Still, it's 2 mins...

Personally, I don't feel comfortable doing practice runs of an activity that has already injured me once. I think I'm not pushing myself too hard; that I can take it, and then all of a sudden the world spins like crazy every time I raise my head. I think I would be able to make it from 130' in a real emergency, but I just don't want to play the odds repetitively against me by doing 2 mins breathholds.

I like to leave the free ascent option for last or near to last in case of real emergencies. That leaves redundant gas supplies. I almost always dive manifolded doubles even in recreational dives. In dives 130' or deeper I will be slinging one or two additional cylinders. That means that if I have 50% slung under my arm. I just need to get to 70' to get access to that gas supply. And if I have to, taking 2 or 3 breaths of 50% while on my way to 70' will not kill me automatically. I can still breath from a free flowing 2nd stage. I can breath from the wing inflator hose. I can isolate the manifold and go to my secondary reg. The point is, I try to have many options available before I have to resort to doing free ascents. Having options is always good.

 

[Slamfire]

Most trained freedivers discover that that extreme discomfort largely passes and can still extend their time 25-75% (guestimate here, but way longer than I ever thought).

Even before I got injured my Dad used to warn me about getting to that point where you bypass extreme discomfort alarm. He used to tell me that there is a reason to have that alarm within you. If you disable the alarm by sheer force of will, you're threading dangerous grounds -- injury is not that far away. Again, personally speaking, if I am to cross that alarm again, it better be for a good reason. Just practicing doesn't seem good enough for me.

In that lecture of Kirk and Mandy-Rae, one of the first things Kirk mentioned is that under certain conditions scuba solo is a manageable risk. Freediving solo is not. Blackouts are just way too common even after you have surfaced and within the first 3 breaths.

 

[MXGratefulDiver]

That is a value judgment. Emptying your lungs means a lot of different things to different people. Are you saying a forced exhalation to try to get the most out you can or the bottom of a normal exhalation cycle?

As far as survival in a worst case scenario, it probably does not make that much difference. You will be exhaling before reaching the surface in any case. Your blood is normally oxygenated enough at the surface that you have about two minutes before you actually black out from anoxia. A diver’s blood is far more oxygenated and is likely to give you even more time. Not blacking out should not be confused with extreme distress caused by excess CO2 and a stressful situation. Most trained freedivers discover that that extreme discomfort largely passes and can still extend their time 25-75% (guestimate here, but way longer than I ever thought).

Scuba divers performing a free ascent have it much better than freedivers, which is what most divers try to equate to. Due to hyper rather than hypo oxygenation and reduced CO2 concentrations, the free ascent is many times easier.

If memory serves, my “this ain’t so hard” moment was after my first 30’ free ascent. I was in Scuba class in Monterey and 11 years old in 1962. I had a hell of a time freediving to 30’ earlier that same day, even though I could comfortably swim the length or a 75’ pool on one breath. On reflection, my Scuba instructor was a superb guide to self-discovery.

No ... I'm suggesting that you try it at the end of a normal exhale ... as though you go to inhale normally, and there's nothing in your tank to breathe.

Theory is great ... but I'm a big believer in not thinking I can do something until I actually try it. Oxygen isn't what drives your brain to want that next breath ... CO2 buildup is. Unless you have something in your lungs to expel the CO2, it's gonna be continuing to increase in your system until you reach the surface. Personally, I know I can do a free ascent from much deeper depths if I'm exhaling the whole way up than I can if I start with little to nothing in my lungs to exhale while ascending.

If you're gonna "trust" your ability to free ascend from 130 feet in an OOA situation, it would be a really neat idea to test the theory under worst-case conditions. You may, in fact, be able to do it ... then again, you might not be. People have a tendency to overestimate their abilities ... sometimes it causes them to die.

... Bob (Grateful Diver)

 

[Akimbo]

No ... I'm suggesting that you try it at the end of a normal exhale ... as though you go to inhale normally, and there's nothing in your tank to breathe…

As mentioned, it probably doesn’t that make much difference due to expansion. My comment was more about defining “emptying your lungs” for others who may read this. I encourage everyone to practice free ascents, starting shallow of course, at different exhalation levels to determine for themselves what impact it will have to their individual performance.

Expanding on the concept for others who read this: You can’t start a free ascent with lungs very full at all… air will just leak out as soon as you open your airway. If you practice opening your airway on the surface, you will begin to sense a level of inflation that is at equilibrium. I have chosen to begin practice free ascents just a little under that level. This is just a guess since I don’t have a spirometer to measure it, but I estimate at or a little under 50% of my normal breathing cycle. Everyone will find their sweet spot.

…Theory is great ... but I'm a big believer in not thinking I can do something until I actually try it…

I could not agree more. That is why I have been advocating starting shallow and gradually leading up to either the point you feel is a personal limit or there is no value in going deeper. That is also why continue to I practice free ascents.

 

[Akimbo]

…In that lecture of Kirk and Mandy-Rae, one of the first things Kirk mentioned is that under certain conditions scuba solo is a manageable risk. Freediving solo is not. Blackouts are just way too common even after you have surfaced and within the first 3 breaths.

I completely agree, but it is a little out of context from my previous post. Hopefully this will make the point more effectively:

People who have not studied and experimented with apnea techniques believe that they are seconds from death when the distress felt while holding their breath is barely halfway into the cycle. For most people, it gets a lot worse long before reaching that threshold where it begins to subside. Even then, they have some time before blackout. Unlike a freediver; a Scuba diver’s blood is hyper, rather than hypo, oxygenated when ascent begins. Hypoxic blackout is a far lower risk.

A Scuba diver practicing free ascents should never let themselves get anywhere near the level of distress that practiced freedivers learn to normally tolerate.​

With practice, each individual will find their own limits, but you can’t just practice in your first year of diving. It usually gets better with experience, and will get worse with age. Trying to figure these limits out in a real emergency free ascent can be a deadly idea. Knowing you are within your limits takes a lot off your mind when things go really wrong so you can concentrate on the problem(s) at hand.

IMHO, knowing these limits is less about ever using the skill than preventing minor problems from escalating into a crisis. Very few solo divers would feel any trepidation if their air supply suddenly and totally failed in 10’ of water. It is nice to actually prove to yourself that you can be equally free of concern in significantly deeper water.

 

[copter53]

. My computer starts whining that I am exceeding 30’/minute. I probably exceed 60'/minute, but not by a lot.

I don't understand this part. I thought you absolutely had to maintain an ascent rate at or slower then 60'/min or else you would get bent?

Here you are saying your standard is 30'/min and even that you don't always maintain sometimes going faster?

Why? Aren't there extra risks here?

What is the advantage of speeding up if any?

 

[MXGratefulDiver]

I don't understand this part. I thought you absolutely had to maintain an ascent rate at or slower then 60'/min or else you would get bent?

It doesn't work that way ... there is no magical line beyond which DCS occurs. The faster you ascend, the higher the risk of DCS ... but at no point is DCS guaranteed to occur.

... Bob (Grateful Diver)

 

[Slamfire]

Here you are saying your standard is 30'/min and even that you don't always maintain sometimes going faster?

Why? Aren't there extra risks here?

What is the advantage of speeding up if any?

You have to keep in mind that the context here is to train for emergency situations. The emergency free ascent is to be used when you no longer have access to breathing gas underwater for whatever reason. You have to get to the surface. So you choose the least of 2 evils: drowning or a higher risk of getting bent.

 

[Akimbo]

I don't understand this part. I thought you absolutely had to maintain an ascent rate at or slower then 60'/min or else you would get bent?

Here you are saying your standard is 30'/min and even that you don't always maintain sometimes going faster?...

To augment NWGratefulDiver’s and Slamfire’s replies, you may find this comment from a related a discussion useful:

… The US Navy’s ascent rate has been 60’/minute for most of my life and there was no such thing as a safety stop. Hundreds of thousands, probably millions, of dives have been made safely during that period. The point is speeding up ascent is highly unlikely to cause decompression problems and preferable to certain drowning. When practicing, make the free ascent at the very beginning of the dive, before you absorb much Nitrogen. Then head back down and enjoy the rest of the dive. The exercise takes a few minutes.

Trained freedivers typically ascend and descent at 1 meter/second, or 200’/minute. That rate might actually get you bent. However the possibility of getting bent is far less of a medical emergency than the certainty of asphyxiation before reaching the surface…

Ascent rates have wondered up and down as decompression theories, statistical studies, and simple convenience interplayed. There was a period before I was born that the US Navy tables were 25’/min. Stories I heard from a crusty old Navy Master Diver who was close to retirement described it as a huge PITA. Picture one of these cigar-chomping old salts with a stop watch watching a pneumo gauge trying to track 2.4 Feet/second or 6.25’ every 15 seconds. Very squirrely.

The sequence I recall hearing was they changed it from 25’ to 60’/minute, in the 1940s or early 50s. 60’/min, or 1'/second, is definitely the easiest rate to deal with. 30’/second was adopted by the US Navy, NOAA, and recreational divers over the last 15 years or so, largely resulting from Doppler bubble studies from multiple research sites.

Why? Aren't there extra risks here?

What is the advantage of speeding up if any?

Consider a free ascent from 60'. That would take 2 minutes at 30’/second or 1 minute at 60’/second. The advantage is you don’t have to forgo inhaling as long. The disadvantage is the added safety margin to protect against bubble formation is gone.

Let’s say you work up a personal best free ascent from 100'. But you have done several repeated successful free ascents from 80’ and feel very comfortable at it. Since this is a discussion about recreational solo dives, you might limit yourself to 60’ without some sort backup breathing system. Someone else may make that limit 30’. Maybe you always carry a completely independent backup and do free ascents as a backup to it. It is fundamentally no different than any other risk calculation we make every day; except this one deals with a generally less familiar environment.

 

[copter53]

This is more a habit from commercial diving than a recommendation. Check for sharpness would be a better phrase for a checklist. A dull knife is worse than no knife. Unfortunately, dive shops sell knives that are dull and most can’t hold an edge. Alas, very few people have the tools or skills to sharpen them anyway.

Well now you have to tell me how to sharpen my knife and what tools to get?