Category Archives: Education and Safety


The fascination with depth among newer rebreather divers has  always given me pause to ponder the thought processes accompanying that fascination.  From a pragmatic viewpoint one could say you go down, swim around and come back up.  Certainly with todays’ technology it is it is not an unreasonable assumption for one to embrace.  Or is it?

Rationalizing that you can successfully manage the challenges presented by deeper dives creates an attractive proposition,  especially for the newly certified, less experienced diver.  It becomes very tempting for them to emulate others who appear to have successfully negotiated the path they are contemplating; one which exceeds their current level of training and experience.
Nothing can be further from the truth.  While on any given day anyone can successfully complete a deep (100 meters plus) dive, when things go awry it is only experience that will save you.

Excursions below 100 meters require more than just meticulous planning.  They require that plus a highly developed skill set which which is created by spending a vast amount of time under the water so you develop the muscle memory necessary to survive.  Skills learned and perfected in a class need to be securely cemented into memory by repetition over time.   Instinct and the ability to spontaneously make the correct decisions under duress are what will permit you to successfully solve problems below 100 meters.  If you have to think about what to do you are probably already doomed.

There was a time when 100 + meter dives were the domain of a small number of divers who had the requisite open circuit skills and were committed to perfecting them.  You needed to manage large numbers of bottles, multiple gasses and often times had to cut your own tables.  Rebreather and computer technology was not yet developed and mainstreamed.  There were no Shearwater Computers nor were there any of the rebreather options available today.

Fast forward to 2020 and almost anyone with the money can buy a rebreather, purchase some training and be doing 400 and 500 foot  (130 – 160 meter) dives in a relatively short period of time.  In most instances s/he will be successful in the endeavor because the technology is so evolved it becomes very easy to become lulled into a false sense of security.    If nothing goes wrong even a chimp can be trained to dive 500 foot depths in a few weeks.  What can’t be done is to train him to react appropriately when things go seriously wrong.  Only time and experience can train that.

So about now you might be wondering what my motivation to write this piece is.  It’s actually quite simple and straight forward.  Over the past few years I have been seeing people on rebreathers routinely diving beyond the level of their training and knowledge base and far more importantly, beyond their experience levels.  Because you have a certification does not mean you have the experience or the knowledge to recognize a bad dive plan, especially when it is proposed by someone you perceive to be an expert.  Certification only gives you the opportunity to learn and expand your skill set so you may evolve and get the experience.  It also gives you the opportunity to make bad choices and does not always prepare you to recognize poor planning.

For instance I have been hearing tales of divers running outrageously high ppO2’s on below 100 meter dives as part of an effort to reduce the decompression obligation.  This is a divers form of Russian Roulette.  Because you won yesterday does not mean you will win today.

All of us participating in this type of advanced technical rebreather diving have at the very least, a bit of Type A personality.  We all like to push the envelope.  It is part of our persona and that is fine as long as we never let it morph into recklessness.  There is a huge difference between managed risk and normalization of deviance.  All too often risk is dismissed because we succeeded in the past so the appropriate precautionary steps are overridden by unrealistic expectations of a successful outcome.  Goal oriented enthusiasm  should never override critical evaluation of what we are about to participate in.   The goal will often be accompanied by tunnel vision that cloaks any risk mitigation analysis you may have done.

So, in summation there are questions one should ponder before engaging in any serious deep rebreather dive.

  • Is the risk worth the reward?
  • Am I willing to gamble my life for it?
  • Is the plan viable?
  • Are there appropriate safety measures in place?
  •  Were I to experience a total equipment failure could I survive it?
  • Is my skill set such that I am confident in my abilities to manage any problem that might come my way?
  • Am I confident in my abilities to efficiently render assistance to a distressed team member?
  • Am I confident in the abilities of my team members?
  • Am I able to competently deal with any DCS issues and is the necessary equipment available to do so?

There is no set of correct answers to the above questions.  These are only thoughts divers should ponder before undertaking any extreme depth dives.  I truly believe in freedom of choice and if the risks are acceptable to you I say go for it.  My only caveat is to know exactly what you are getting into before you commit.

Loop Leaks and Water Intrusion

Leaks are bad, no matter if they are in Congress or in your rebreather loop.  They are annoying and dangerous.
Prior to diving we should all use a check list and do our pre-dive checks, two of which are the “positive and negative” tests.  Their purpose is to detect system leaks  before entering the water.  We pressurize the loop for a positive test and draw a vacuum for a negative test.  We then look for changes in counter lung volume and or listen for hissing sounds.  If they deflate, inflate or hiss we suspect a leak.  If they hold pressure and are silent we say they passed and are safe to dive.
But, are they?  It is quite possible you have a leak that eludes this process.
The Mouthpiece
Probably the most common leak is from a split or torn mouthpiece.  It can also be quite difficult to find.  A tiny tear or hole in a mouthpiece can present quite the mystery.  The loop will pass positive and negative testing and seem fine. Then, during the dive you hear that ever so annoying “gurgling” sound.  You listen for bubbles and hear none.  You signal your buddy to check above you looking for leaks and he tells you there are none.  But you keep draining the water from your loop so it has to be coming from somewhere.  To further complicate things, the loop might only take in water on inhalation or when you tilt your head in a certain position.  You may look for the leak on every exposed part of your rig and not find it. 
So what Do You Do?
If you are getting water in your loop and cannot find the source, even after checking all of the prime suspects, change the mouthpiece, even if it looks good.  This will often solve the problem or at the very least eliminate the mouthpiece as its’ cause.  Sometimes the leak is so minuscule that only an exaggerated stretch, bend or twist will reveal the tear or pinhole.   
Sometimes the cause of the leak is not a tear or a pin hole.  Believe it or not, if your DSV or BOV is angled incorrectly it will cause the side of your mouth to twist open when you move in certain positions and allow water in.  This could potentially cascade into a very unpleasant event if it causes the loop to pop out of your mouth.  If you are fighting your loop to keep it in your mouth straight it needs to be adjusted to fit you properly.  Loosen the hose clamps and move it so it sits at the same angle as your mouth and does not pull up, down or sideways.  Of course be sure to retighten the hose clamps properly.
Loop Hoses
A small split in the crevices of a loop hose can be very difficult to find.  It may only leak when the hose is stretched or turned in a specific way.  All other times it may be fine.  Because of this it is important to perform a visual inspection of your hoses as part of your pre-dive ritual.  Do this when you check your mushroom or flapper valves by stretching the hose.  Look for cracks or splits in the crevices between the ridges and where they are clamped to anything (DSV, TEE Pieces etc.).    Anything suspect should be visually inspected and tested with a soapy water bubble test or by submersion.  Remember, this type of leak can easily pass your standard positive and negative testing, so while I am not suggesting it is something to be paranoid about, it is not something to ignore.  This is why I do not like hose covers.  They may look cool but can conceal dangerous leaks.  High quality loop hoses are quite robust and do not need covers.
Be wary of rubber sleeves covering loop hose clamps.  They make the loop look pretty but they can conceal a large tear.  In the image below the loop hose was torn by the clamp but it passed a positive and negative test because the clamp was covered with a rubber sleeve which in effect, sealed the leak.
Should you find yourself in the water with this type of leak, the safest solution is to bail out.  If that is not practical or possible, an alternate solution is to grasp the hose with both hands and hold it in a position where it doesn’t leak, IE, press the offending crevice together to stop the leak while you abort the dive.  Obviously, this is only practical in a limited number of circumstances where the split is small and in which staying on the loop is a better choice than bailing out.  Remember, a flooded loop can lead to a caustic cocktail and cascade into a series of very unpleasant, potentially fatal events so if you make this choice, do so judiciously.
The next source of leaks and water intrusion are orings.  They should be inspected every time you build your unit.  Change any orings that have flat spots, nicks or cracks.  Lubricate any orings that require it but don’t over do it.  Remember that lube is also a dirt magnet so use care to not pick up any grit while the orings are exposed to the environment.  Also visually inspect oring grooves and clean any accumulated dirt or excess grease.  If necessary, remove the oring and clean the groove.  Use a plastic pick or something similar for removal to help prevent accidental damage.
Every rebreather diver should be proficient at removing water from the loop.  He should also be cognizant of how water will collect in his particular rebreather so he does not do anything to worsen his situation.  For example, if you suspect water is in the unit and proximate to the scrubber you need to understand the unit well enough to avoid positions that will facilitate  water reaching the sorb.  I will not go into specifics here because every unit is different.  What works well on one unit might be bad on another.  If you do not understand this process well or if you understand it but are not good at it you should remedy this deficiency as soon as possible.  Practice the procedure often so it becomes second nature.  If you do not understand the path necessary to facilitate water removal, call your instructor and ask him to clarify it for you.  Once you thoroughly understand the flow of the unit, dewatering becomes very simple.  If your rebreather does not permit removing water from its breathing loop you need to account for that in your dive planning and factor in extra conservatism to account for it.  Avoid dives or situations where the probability of water ingress into the loop is higher than usual and access to the surface is limited.  You don’t want a flood 5000 feet back in a cave with no well rehearsed plan of escape.  Remember that a flooded unit becomes extremely negative, making swimming on open circuit bailout more difficult.  Even if you can no longer stay on the loop, the ability to remove water from it is important.
The Best Leak Test
 So, what is the best leak test?  At the beginning of every dive buddies should hover above one and other and look for bubbles.  The predive positive and negative tests will find any larger leaks but nothing surpasses an in water bubble check at depth to find any smaller leaks.  This can be accomplished at 20 feet in conjunction with a cell linearity check.  If this is not practical do it at depth before you begin the actual dive.  In any event, this should always be done.  Other indications of a leak include gurgling sounds in the loop, hissing noises behind your head, an unexpected change in buoyancy or an increase in the work of breathing.  The silence afforded us by diving a rebreather permits hearing the smallest of leaks so be acutely aware of any unusual sounds.  Do not ignore them.
I hope some of you, especially newer rebreather divers, find this information useful.
Until the next time, thank you for reading.


The Ring of Death

Over the years I have come to realize that in this sport we all love so much every diver is responsible for their own safety and well being.  The notion that anyone else will care about or protect you as well as you will do for yourself is flawed.  It won’t happen, which of course begs the question; how does one effectively ensure safety?

You Don’t Need A Crystal Ball

You need a little common sense which unfortunately, is often times not so common.  Most events having negative outcomes are usually highly predictable.  They have signs that are like billboards once we learn to recognize them.

Beware Of

Advanced tech dive trips or projects that are in search of participants.  They are always suspect.  If it is such a good trip or project why isn’t it filled?  The good ones fill up as fast as they are announced.  If the only requirement to get on an advanced Tech trip or participate in an advanced project is a certification card you should be wary.

Right about now you might be asking yourself, “Why is this so?”

Well, the answer is simple.  Tech trips and projects require larger numbers of qualified divers to make them viable.  By industry standards the only requirement is that participants hold the appropriate certifications which of course say nothing about experience levels.  It is only the level of human decency the organizers may or may not have that dictate how well they vet participating divers.  A well organized, safely run trip or project will always incorporate some sort of vetting process before divers who are unknown entities are allowed to participate.  Be happy when an organizer asks for a reference to vouch for you.  It means someone cares about the project or trip, you and your family.  They don’t want to make the phone call that all team leaders dread.

If you have no one to vouch for your abilities and experience level, DON’T LIE!  There are not that many participants at this level of diving.  Everyone knows everyone else and a good team leader will be able to vet you by who trained you and who you dive with.   You will fare much better by telling the truth and saying that you’d like to participate and would be happy to go on a benign “shakeout dive” to demonstrate your abilities.

It Works Both Ways

Just as trip and project organizers should vet you, it is in your best interests to vet them.  While anyone can have an accident or a bad day, if you pay attention you will find that whenever there is a negative event it is often the same people, places and operations that keep popping up.  Learn to recognize them and judiciously avoid the “Ring of Death”.   Don’t be afraid to question procedures and protocols.  Review their track record.  Is there a history of avoidable accidents?  Is there a history of incidents occurring because participants are diving past their experience levels?  If so, walk away.  If they don’t seem safe they probably aren’t.  The Wreck, Cave or whatever will be there for a long time.  There is nothing worth losing your life or your health to see there.

If It Sounds Stupid, It Probably Is

Learn to listen to that inner voice we all have and don’t be intimidated by someone who is vastly more experienced than you if the proposition sounds stupid.  You are probably right so don’t be afraid to ask questions and walk away if you don’t get satisfactory answers.  Often times there is a desperation to fill a boat or run a project dive and when the organizers can’t attract their “preferred” participants they open things up to anyone with a certification and dollars.  You might be tempted to think “Well I know I am experienced enough to do these dives so it’s not a problem for me”.  Well, it is unless you have no heart or soul.  I would like to believe that all of us would render assistance to a fellow diver in trouble even if we otherwise don’t know or even dislike the person.  By default this puts you in harms way.  The possibility of a panicked diver taking others to the hospital or grave is very real.  It is in your best interests to recognize that fact.  You don’t want to be surrounded by well meaning people who are diving beyond their experience levels.  If they have a problem you are most likely going to render aid and be in jeopardy.  The best option is to not be there.  Twice in my life I “dodged the bullet” this way.  Both times I was scheduled to go on a trip and when I heard who was going and what they were doing I suddenly had a scheduling conflict.  Both times there were fatalities.  My ego likes to believe had I been there those accidents would not have occurred; that I would have seen them coming and prevented them.   The realist in me knows that is not so.  You can’t save the world.

So, the next time you want to dive on a Tech trip or project, or do advanced dives with a group unknown to you, it is in your best interests to vet them first.  If all you need is a certification or the necessary dollars, run away.  If no one asks for your diving resume, run away.  If the operation or group has a dismal safety record, run away.  If you keep these “rules” in mind you will increase the odds of not being in or near the “Ring of Death” and enjoy many years of safe diving.