Ever experience a SWB?

[freediver]

Here's my list of do's and don'ts. I want to give these in order that someone might be spared in the event of a b/o. If anyone has any modifications or additions that would be great. I by no means know everything nor do I claim to.
NEVER DIVE WITHOUT A COMPATENT BUDDY
USE THE ONE UP ONE DOWN RULE. MEANING WHILE ONE PERSON IS DIVING THE OTHER WAITS ON THE SURFACE IN CASE A RESCUE IS NEEDED.
PLAN YOUR DIVES. TELL YOUR PARTNER HOW LONG YOU PLAN TO BE DOWN. DON'T GO BEYOND WHAT YOU DISCUSSED.
IN LOW VIS SITUATIONS OR SWIFT CURRENTS , USE A DIVE LINE. DON'T STRAY FROM IT. IT'S WISE TO USE A WRIST LANYARD IN CASE YOU DO B/O YOUR BUDDY CAN FIND YOU.
DON'T DIVE BEYOND THE DEPTH YOUR BUDDY CAN. IF YOU NEED RESCUED AND YOUR AT 20 METERS BUT YOUR BUDDY CAN ONLY REACH 15, YOU'RE A DEAD DUCK.
NEVER, UNDER ANY CIRCUMSTANCES, HYPERVENTILATE. TO HYPERVENTILATE IS TO "BLOW OFF" CARBON DIOXIDE. CARBON DIOXIDE BUILD UP IN YOUR SYSTEM IS WHAT TELLS YOUR BODY YOU NEED TO BREATHE. IF YOU PURGE YOUR SYSTEM OF CO2 YOUR BODDY WILL NOT KNOW WHEN IT'S TIME FOR YOU TO BREATHE. BY THE TIME THE CO2 BUILD UP REACHES THE POINT TO GIVE YOU YOUR URGE TO BREATHE YOUR OXYGEN RESEREVE IS USED UP AND THE BODY SHUTS DOWN CAUSING A BLACK OUT.DON'T BREATHE EXCESSIVLY FAST OR DEEP. A GOOD RULE OF THUMB IS TO JUST BREATHE NORMALY AND THEN TAKE ONE LAST DEEP BREATH BEFORE SUBMERGING.
USE A QUICK RELEASE WEIGHT BELT. IN CASE OF TROUBLE DITCH THE BELT AND SAVE YOUR LIFE.
DIVE WITHIN YOUR LIMITS. EVEN IF YOU "FEEL GOOD" AT DEPTH BE AWARE THAT YOU USUALLY WILL DUE TO THE PRESSURE AND BLOOD SHUNT. WATCH YOUR TIME AND DON'T GO OVER.
DON'T FOCUS ON GOALS. OR DON'T SACRAFICE SAFTEY FOR A FISH OR FOR THAT EXTRA METER. IT'S NOT WORTH IT. BE AWARE OF HOW LONG YOU'VE BEEN DOWN.
KNOW HOW TO REVIVE AND RESUSITATE (SP?) A B/O VICTIM.
MAINTAIN PROPER SURFACE INTERVALS. DON'T STAY DOWN FOR TWO MINUTES AND COME UP FOR ONE. GIVE YOURSELF AT LEAST TWICE THE TIME AT THE SURFACE AS YOU DO AT DEPTH. IT WOULD BE WISE AND ADVISABLE TO GIVE YOURSELF FOUR TIMES THE SURFACE TIME AS DEPTH TIME.
IF YOU ARE OVERLY TIRED OR UNDER THE WEATHER, DON'T DIVE THAT DAY. IT CAN BE DEADLY.
THESE RULES ARE MEANT FOR RECREATIONAL FREEDIVERS AND SPEARFISHERMEN.

Sorry to be so long winded.
God bless and safe dives,
Stitch

Wow Bindlestitch! That about sums it up. i will add just a couple:
* Make sure you're correctly weighted.
* Never force an equalisation and abort the dive if equalisation ever fails.
* Never freedive after a dive on SCUBA.
* Remove snorkel for duration of dive!
* Use appropriate lines and/or rigging.
* Rapid "turn arounds" should be avoided, this has been implicated in some "deep water blackouts".
* Refrain from looking down on descent and up on ascent.
* Stay hydrated!!

 

[Bindlestitch]

Wow Bindlestitch! That about sums it up. i will add just a couple:
* Make sure you're correctly weighted.
* Never force an equalisation and abort the dive if equalisation ever fails.
* Never freedive after a dive on SCUBA.
* Remove snorkel for duration of dive!
* Use appropriate lines and/or rigging.
* Rapid "turn arounds" should be avoided, this has been implicated in some "deep water blackouts".
* Refrain from looking down on descent and up on ascent.
* Stay hydrated!!

Freediver,
All excellent advice. The rule about correct wieghting you mentioned is spot on. It's something that people don't often think about until they start for the surface and find out they're carrying to much weight. And by then it's sometimes to late.
God bless and safe dives,
Stitch

 

[plongeursousmarin]

I did once and it's a textbook case of what NOT to do while freediving. I was spearfishing solo in Italy (island of Panarea), far from shore (about a 400 meter swim including crossing a ferry path!). I was coming back up from about 18 meters, had been down for maybe 1:30 minute but I saw a fish below as I started my ascent and turned back down like a moron to investigate where it went. I resumed the ascent but started feeling the urge to breathe but there was still 3-4 meters to go and then everything went black and when I surfaced my head was spinning and I felt like I was completely upside down or something. Scariest feeling I've ever had. Needless to say that was it for that day as I knew I had escaped death by maybe a handful of seconds.

 

[vladimir]

Refrain from looking down on descent and up on ascent.

Why?

 

[freediver]

Why?

Hey vladimir, what happens when you look up or down during the dive, you are hyperextending the neck and it has a tendency to compress the arteries that supply the brain with O2 enriched blood. This is something we do not want to occur, esp. since with ascent the reexpanding lungs tends to pull O2 away from other areas, ex..the brain. Does this make sense?

 

[vladimir]

Yes, thanks.

 

[rgbmatt]

Of course the downside of not looking up is that you might bump into something on the way!

Because of this, I've poked myself in the head at least twice with my 3-prong (clipped to my float) and once I headbutted a turtle. But at least it wasn't a motor skeg or something like that

 

[fishnchips]

Thanks all for sharing valuable knowledge about swb. I've been on SB for sometime and IMO, I've gained the most valuable knowledge from this thread. Thanks again.

 

[freediver]

Thanks all for sharing valuable knowledge about swb. I've been on SB for sometime and IMO, I've gained the most valuable knowledge from this thread. Thanks again.

hey fishnchips, great to hear that. Here is a bit of clarification in terms that i have researched and found from some of the experts in freediving physiology. There are three different types of blackout associated with the sport of freediving. They are:

SHALLOW WATER BLACKOUT -- a state of unconsciousness preceded by carbon dioxide retention. Unconsciousness strikes most commonly within 15 feet (five meters) of the surface. This is generally what happens to the person that swims long horizontal distances as the CO2 builds up in the body.

BREATH-HOLD BLACKOUT -- a state of unconsciousness preceded by the gradual onset of hypoxia; risk is compounded by hyperventilation or increased (shallow) underwater activity. Generally occurs to those that are practicing static breath holds.

ASCENT BLACKOUT -- a state of unconsciousness preceded by sudden onset of hypoxia during ascent; risk is compounded by hyperventilation or increased (shallow) underwater activity. This is what most refer to as Shallow Water Blackout. It is actually termed Ascent Blackout as the diver ascends and , upon expansion of the lungs, vital O2 is taken away from the brain and utilized by the lungs. A rapid ascent may increase liklihood as well as exhalation on ascent. Unlike Scuba, exhalation during the entire ascent is not stressed. It is only within the final 5m - 8m that the diver should start to exhale.

Hope you can find this useful.

 

[Stirling]

I'm not too clear about exactly what the differences are between the three types of blackout just described.

When I first started diving a lot (before taking up SCUBA), I practiced swimming laps under water in a swimming pool to improve my breatholding capability for pretty shallow freediving in the ocean.

I overextended myself several times in the ocean by staying down too long and almost running out of time on the ascent, but without experiencing any kind of blackout. By the time I got to diving in the ocean, I had learned about the risks of hyperventilation and didn't do it in the ocean. In my defense, I was a teenager and this was before information about such things was as readily available as it is today with the Internet and everything.

Before that, I had tried using hyperventilation to extend my breathholding ability swimming laps submerged in a swimming pool, and came close to experiencing shallow water blackout just as I was breaking the surface to breathe. What happened was like instant tunnel vision, with the lights suddenly going out, but in my case it didn't happen until I was becoming desperate to breathe again and was already coming to the surface. I have read of other cases where people have blown down the CO2 level in their lungs by hyperventilating (or maybe using other methods I don't know about) to such an extent that they pass out from hypoxia before the urge to breathe again is really strong in them.

I don't think the problem is freediving or breathholding so much as it is using dangerous methods - hyperventilation probably the most common and the worst among them - to try to extend your range beyond your actual abilities. People who really know what they're doing can (obviously) dive well beyond anything most of us could ever attempt. It's always most dangerous at amateur hour, when a beginner's enthusiasm crowds out good judgment.