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Blast clearing snorkle

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cliffgollus

New Member
Feb 22, 2003
32
4
0
The article Safety Tips for Freediving indicated one should remove the snorkle from your mouth before diving. One reason given was that "blast clearing" of the snorkle at the surface "almost invaribly leads to SWB if a diver is near there limit". I have never heard this before and have always blast cleared at the surface so as to get fresh air asap. Any thoughts pro or con from the forum?

Also, one tip was, "do not look down during descent". What about spear fishers? Or simply someone diving on coral heads? Do most people differentiate between freediving (as in spearfishing) and freediving (as in competition)?

Thx, Cliff
 

M-2

New Member
Jun 28, 2002
184
18
0
50
Hey Cliff! While I can't speak for those that made the statements that you're referring to, I can add some thoughts on the subjects. Another reason for removing a snorkel while freediving is that if you do blackout with the snorkel in your mouth your airway is open to water coming in. With the snorkel out of your mouth the airway is more likely to stay closed and keep water out. This can make a big difference in recovery from such an event.

With respect to not looking down you have to use common sense. If you need to look to see where you're going then by all means look. But in competitions or attempting very deep dives straining to look down adds exertion and adds stress to your airway.

And yes, the competitive divers, spearos, and others do tend to emphasize different things or have different approaches based on their purpose, so it's always good to keep that in mind.

Hope this helps!

Cheers,

Mike
 

cliffgollus

New Member
Feb 22, 2003
32
4
0
I appreciate the replies, please excuse my ignorance, is SAMBA the same as SWB (shallow water blackout)? My understanding of SWB is that as you surface, pressure drops, lungs expand, and because the oxygen in your lungs has been already depleted, there is a sudden drop in oxygen partial pressure in the blood leading to blackout, often without warning. How can this condition be delayed by not forcefully blasting water out of the snorkle and getting fresh air into the lungs? If anything, forcefully exhaling would seem to momentarily raise pressure in the lungs and perhaps (although insignificantly) O2 in the blood.

Allow me to be more specific as to my interest. When spearfishing, one is repeatedly diving, surfacing, clearing the snorkle, rest a bit and do it again. Are the better spearfishermen doing this without the snorkle in their mouth? Raising the head above water to get air would seem a huge waste of energy! The initial post incidently was in response to the current article on Deeper Blue re: 10 or 20 safety tips.

Thx for your input and patience,
Cliff
 

Skindiver

100 % H2O
Feb 5, 2002
267
40
118
Samba

Your description of SWB is accurate enough.
Samba is a loss of motor control without a loss of consciousness. You shake or 'dance'.. hence Samba.
One can take it that in a case of SWB you dont make it to the surface, unless you float up with luck and good weighting.
With a Samba you obviously did make it to the surface by your own volition and propulsion but on reaching the surface you suffered a shake. This can degenerate into a blackout if severe enough.

One reason given was that "blast clearing" of the snorkle at the surface "almost invaribly leads to SWB if a diver is near there (sic) limit".

Normal repetitive diving should not bring one close to the limits where you are on the verge of losing consciousness or a loss of motor control.

Many spearo's will spit out the snorkel before diving but not really for the reasons of avoiding having to blast clear it. They do this to flood it so to avoid bubbles trickling out and scaring the fish. These divers usually replace the snorkel on the ascent and release a small amount of air which expands on the ascent driving the water out and leaving the diver with an already cleared snorkel as they surface.

Other divers exhale on the way up in the last 5 - 3m. These guys believe they decrease the O2 'vacuuming' effect - for if there is no / less / little, air in the lungs it cannot suck much air from the blood- decreasing the possibility of SWB. Others do it to get the exhaling part over and done with and clear the snorkel for free with no effort, by the action of the escaping and expanding air.

As for a blast increasing lung pressure, it might briefly but its increasing pressure of stale air. Not much use to anyone. A hook breath on the other hand increases pressure of the good stuff. That good stuff incidently takes 10 - 15 seconds to hit the brain where its needed. This is why sambas often are a bit delayed. The poor stuff also takes 10 - 15 sec to hit the brain and switch it off.

I suspect that the reason that a forceful exhale may induce a shake is the effort that goes into the blast may rob the last critical bit of oxygen as well as and prolly more importantly, the pressurisation of the lungs and contraction of resultant rib cage muscles and diaphragm may exert a pressure on the heart and arteries carrying by now oxygen poor blood to the brain, slowing or even interrupting the oxygen depleted flow for a second, enough to cause the mainframe to blink and you lose your wallflower status .. The dance is on.

Dont worry about blast clearing your snorkel. Do it. If you are on the limit you will have forgotten to drop your weightbelt and will blast away when you hit the surface anyhow, as you will more than likely not be too cogniscant of your actions at that time. Surfacing and spitting out your snorkel to avoid clearing as a routine it is not an option.

Under those circumstances i would prefer you have the snorkel in your mouth because if you samba and black out you may just end up face down, blasted snorkel in and a clear air passage and auto recover. Without the snorkel you would be very lucky to end up on your back.

Some say that a SWB with snorkel in is bad cause the water flows into the mouth directly through the snorkel.
I dont think this is so because the mechanism that keeps the mouth closed also keeps the tongue jammed into the mouth of the snorkel and the soft palate and the tongue together, stalling any water ingress until this inevitably also releases at the time the closed mouth would have relaxed and opened anyhow.

Skin
 
Last edited:

cliffgollus

New Member
Feb 22, 2003
32
4
0
Thank you for a great reply! I have the Terry Maas book Freediving and Spearfishing ordered (has taken about 3 months to get!) and hope to learn more about these things from the book. Your thoughts on floating at the surface, perhaps unconscious but with a cleared snorkle, reinforce the importance of proper weighting so as to be positively bouyant for the last 5-10 meters. The idea of letting a bit of air into the snorkle on the way up so it will expand and "self-clear" the tube is something I will have to try. I might also add I do not really "explosively" exhaust the snorkle, I typically try to clear it just as I break the surface with as little effort as possible.

A question, is SAMBA a precursor to SWB, or a totally different manifestation? I have experienced what I believe to be a close brush with SWB but never SAMBA. Does SAMBA effect some people but not others? Any thoughts on why one occurs vs the other? If anyone else reading these posts has experienced SAMBA, perhaps they could relate the experience and share their thoughts.

Thx, Cliff
 

Skindiver

100 % H2O
Feb 5, 2002
267
40
118
Samba / SWB

Samba is a loss of motor control caused by too little oxygen available for the brain. One of the first faculties to 'go' is the laying down of memory, then a loss of motor control and then blackout. Your hearing lasts the longest even into unconsciousness.

This is why many that samba and black out wake up demanding to know why they are being held and what this funny oxygen mask is doing on their face !! They are fine !! Also its why someone shouting to you to breathe or remove your mask is effective even after you are for most intents - out.

SWB occurs underwater or on surfacing suddenly but is as a result of the process you described in you post, and without warning. You generally dont shake. You just go .. stop... Off... Swimming off.. thinking off.

You have demonstrated that you have a good idea why this happens. One second there is enough oxygen, the next there is not. Its not gradual for the most part. Anyone can samba or SWB. No one is immune.

Whilst I imagine that a shake could experienced on ascent to some extent prior to SWB , their their mechanisms of oxygen starvation differ, and for all intents and purposes SWB is not recognised as being preceded by a Samba.

SWB cannot by virtue of its description happen without a dive.
Samba can precede a surface blackout.
A surface blackout can also happen bypassing samba. Similar to SWB but with a different mechanism by excessive Hyperventilation. Hyperventilation can turn blood so alkaline that the urge to breathe is set way beyond the loss of consciousness level. The participant blacks out without shaking or trying to recover or even realising he was in dire straits.

Skin.
 

cliffgollus

New Member
Feb 22, 2003
32
4
0
Thank you for your reply, much appreciated! Your comments on blacking out are very interesting and should be carefully remembered. My personal experience was almost exactly what you describe; eyesight gone (gradual but complete, like a cloud coming over you until all is dark), then hearing diminishing - but even at this stage still "conscious" in the sense of able to think.

I think what scares me is that one can be feeling good, diving well, going just a bit deeper or longer, and end up blacking out just short of the surface. If that happens, will the choking reflex "bring you back" long enough to get a breath of air? This is not much of a consolation since salt water down the "wrong pipe" burns like fire and can make you instantly extremely sick (we had a guy drown this way).

Thx, Cliff
 

cdavis

Well-Known Member
Jan 21, 2003
4,006
779
218
71
samba

Skin, thanks for your excellent posts. The additional comment helps put the safty artical in better perspective.
You mentioned that memory goes early in a samba event. My known experiance with samba was early in my diving experiance but I have stayed down too long more times than I care to admit. Is it possible, likely?, that I, and other divers, have experianced mild sambas and not remembered them. If so, this puts a whole different perspective on the need for a buddy at all times.

Connor
 

Skindiver

100 % H2O
Feb 5, 2002
267
40
118
Choke reflex.

Laryngospasm.

The throat will auto close especially when the first trickle of water hits it. This will last for 30 seconds or so and then will relax and permit the ingress of water.

The laryngospasm will not bring you around. The only thing that will do that is Oxygen. Laryngospasm will delay the ingress of water , and if you are lucky and floating upwards it will buy some time.

I have heard it theorised that on SWB a sinking victims lungs repressurise owing to the increasing water pressure and this may happen to the extent that the partial pressure of oxygen increases enough again to permit regaining consciousness. The victim may once again start for the surface only to encounter the same fate again ...
It would be an extremely competant victim that could overcome the disorientation of almost certainly blown ears ( due to no compensation whilst passed out ) waking up from SWB and dropping a weight belt to attempt an auto re - surfacing and recovery during this stage.

If you samba'd i'm sure you would know it now knowing the symptoms. You would not be able to judge the severity of it.
Unless you have hyperventilated to distraction you will surely have intense feelings of oxygen starvation discomfort preceding Samba and or SWB. These things are less likely to strike on a good comfortable dive ascent.

Be aware and prepared, but dont be scared. Understand the mechanisms but have a positive mindset. Dont dwell on SWB and Samba. Surface with some to spare. If you push you best have a full safety diver team in the water to pull you out if you over cook it.
If ever you feel like you are fading, fight it.
Try stay awake.
I have fought to retain my vision as it closed in on me and won just by refusing to let it go. Staring hard, shaking my head clear and focusing on keeping it together and getting out of the situation i have landed in. Keep thinking after the curtains close. If you are prepared it will be easier to survive.

I spearfish too and if i spend a minute underwater on each dive its a alot. Its just not comfortable for me to stay down longer. But I might dive twice as much. So whats the difference ?

Skin.
 
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