Hawaii Skin Diver The Breath of Freedivers

Shallow water blackout seems to be causing why too many deaths recently. Here is an article with some safety tips to take a lot of the danger out of freediving.

Though news of coastal shark attacks seem to preoccupy the media lately, there's something even more dangerous--and a lot more common--that gets much less notice. Its name: shallow-water blackout, a condition which commonly results in death by drowning. This is a very important topic this time of year as our Florida waters are teaming with divers looking for the tasty spiny lobster.
Shallow-water blackout often affects free divers and skin divers (those divers without any sort of breathing apparatus other than a snorkel). I used to think the only dangerous kind of diving was with tanks or compressed air because I had heard of and seen so many disastrous outcomes. However, studies have now shown that many fatalities among experienced divers and swimmers have occurred simply from free diving. Some medical experts believe many of the backyard pool drownings are caused by the physiologic changes that result in shallow-water blackout.

WHY DO SHALLOW-WATER BLACKOUTS HAPPEN?
It really is all about physics and gas pressure in the lungs, so here are the nuts and bolts. First, we all know we need oxygen (O2) to live but the body uses our levels of carbon dioxide (CO2) to tell us when to breath.

Most of us deplete our O2 stores more quickly than we build up CO2. This is even more pronounced in experienced divers who can hold their breath for longer periods of time (at least more so than us out-of-shape individuals).

Second, the deeper you are in the water, the more compressed the air in your lungs will become and the more concentrated the oxygen you are able to use.

As you rise in the water the lungs expand resulting in the decrease in concentration of usable oxygen. This expansion of the lungs is more pronounced as you reach 15 feet of the surface and continues to progress as you ascend in the water column. In effect, what can then happen is that your brain becomes starved of precious oxygen and you may blackout. Unless you are helped to safety immediately, you will drown.

WHO IS AT RISK FOR SHALLOW-WATER BLACKOUT?
As a rule, we all are at risk for shallow-water blackout. Statistics have shown, however, that shallow-water blackout tends to occur more often in experienced divers as well as younger divers. This may be due to experienced divers having become accustomed to ignoring that burning sensation in their lungs longer thus leading to lower levels of available oxygen as they attempt to surface.

Pre-dive hyperventilation is thought to be another dangerous practice that predisposes us to shallow-water blackout.

Just visiting any pool with a bunch of kids competing to see who can stay under the longest can show you this breathing practice when preparing to dive.

Physiologically it makes sense. Several deep breaths with prolonged expirations actually allows you to blow more carbon dioxide from you lungs thus staving off the sensation of needing to take a breath a little longer during a free dive.

Unfortunately, hyperventilating in this manner does not put more oxygen in the lungs and can lead to disastrous results. The U.S. Navy Diving Manual recommends hyperventilating no more than three or four breaths prior to a free dive for the same safety reasons.

Divers who use weights to descend--as well as spear fishermen and our lobster grabbers--are also at special risk because they will likely become focused on their prey and exhaust their oxygen supply beyond safe levels. Thinking "just a few more seconds" puts these sportsmen at risk of drowning due to shallow-water blackout as they try to surface.

WHAT CAN I DO TO PREVENT SHALLOW-WATER BLACKOUT?
If you are as hard headed as I am and intend to go diving any way, here is a summary and suggestions of what you can do to prevent disaster on what will hopefully be a fun day on (and under) the water:
-Always dive with a buddy and be sure to maintain contact while ascending to the surface.
-Do not hyperventilate more than three to four breaths (if at all) before diving.
-Do not over-exert yourself at depth.
-Pay attention to that burning in your lungs. Your body is trying to tell you something: "I need air!"
-If you wear a weight belt, make sure it includes a quick release mechanism.
-Avoid a competition with your buddy to see who can stay down the longest. You both may end up being down longer than either of you intended!
-Know basic CPR. (We should all be trained in this anyway.)
-Know your depth and realize the risks of shallow-water blackout increase as you ascend. This is especially true as you ascend to within 15 feet of the surface.
-As always, be safe. Live to fish another day!

Thanks for posting bro!

thank you for posting, i am not sure that your advice of not to wear a weight belt works for speros, we need the weight belt as a matter of fact, i've only been diving for 8 years and have taken the PFI II class and yet to see a serious spero who wears a wetsuit and dive without a weight belt.

PAUL!!!

Yeh i know what you mean. It was late at night and i was tired and felt strait foward and strict when i wrote this lol. I changed the weight advice to if you have a weight belt make sure it includes a quick release mechanism.

here you go trying to prove me wrong by pulling info from another world i was talking about mere humans not THE PAUL

Wow... Smells like a troll to me.

well, it is what it is, the paul is the paul, us mere humans need to be content with our biological limitations while the olympians among us like Paul and Finns can do whatever they want, same polanet, different world. My hat off to all chieveres in free diving who show us what the possibilites are

Umm what exactly is a Paul lol...

Thanks for the post. I've been thinking about this topic for the past few days. You helped a lot. Mahalo!

Oops! My bad. I forgot that THE PAUL crash landed in his ship as a child.

Was looking up something online about another thread on the bends which lead to a wikipedia article on snorkeling which claimed that hyperventilation can lead to shallow water blackout which I'm not sure is correct because theoretically this condition could happen on land in the form of a brownout(?). Is it just that when this happens in the water its automatically shallow water blackout? All that I've learned about shallow water blackouts thus far makes these statements seem imo fallacious.
Further reading into what wikipedia had to offer was this:
The mechanism for deep water blackout differs from that for shallow water blackouts and does not necessarily follow hyperventilation.[3][4] However, hyperventilation will exacerbate it and the two should be considered together. Shallow water blackouts can happen in extremely shallow water; brownouts can be induced even on dry land following hyperventilation and apnoea. However, the effect becomes much more dangerous in the ascent stage of a deep free dive. Refer to deep water blackout for more detail. There is considerable confusion surrounding the terms shallow and deep water blackout and they are made to refer to different things, or used interchangeably, in different water sports circles. For the purposes of this article the two are separate phenomena with the following characteristics:

Deep water blackout occurs as the surface is approached following a breath-hold dive of over ten metres and typically involves deep, free-divers practicing dynamic apnoea depth diving usually at sea.[4] The immediate cause of deep water blackout is the rapid drop in the partial pressure of oxygen in the lungs on ascent.
Shallow water blackout only occurs where all phases of the dive have taken place in shallow water where depressurization is not a factor and typically involves dynamic apnoea distance swimmers, usually in a swimming pool.[3] The primary mechanism for shallow water blackout is hypocapnia brought about by hyperventilation prior to the dive.

can anyone shed some light on what is technically the correct definitions? I imagine they go over the physiology of blackouts in the pfi 2 course.

Being new to the sport and forum, I find myself having several questions. The one for this topic is: If you're going to have shallow water blackout, would it be best if the snorkel was still in your mouth when you passed out, or is it best to spit it out when you dive?

keep the snorkel out of your mouth when you go down. if there is a chance for you to black out and you still have the snorkel in your mouth, your most likely going to breathe in a whole lot of water.

thanks Ryan!