Category Archives: Rebreathers


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.





The origin of this post is a Facebook discussion about lift bags.  After reading all of the varying methods and opinions, I decided to add my thoughts to the conversation.  Those thoughts are here in addition to a few things I did not post on Facebook because they were not germane to the conversation.  I hope newer divers and students will find this useful.

I give preference to 400′ reels with #36 line. The heavier line reduces the length to probably around 250′ or so but the trade off in durability is worth it.  I also avoid reels with complex mechanisms.  Spring loaded snaps, latches or locking mechanisms just add to the complexity of something that should be as simple as possible.  Don’t read this as a condemnation of any particular style of reel.  I just think that a spool in a well constructed frame controlled with a bolt is pretty much as safe and simple as it gets.

I always carry 2 reels and 2 bags or SMB’s (Surface Marker Buoys). I prefer one of each. My SMB’s always have enough lift to get me off the bottom in the event of a catastrophe.   They also have my name on them and the words “Diver Below” so boaters won’t think they are just lost floats.  You should not be able to pull an SMB under the surface once properly deployed.  If you can, get another one.  Bear in mind that while a lift bag may have more lift, an SMB has less drag in the water.  This will make a big difference in strong current.

My reels have bolt snaps tied to the bottom of the handle as opposed to the double enders they usually come with. This is to lessen the chance of losing them and to facilitate clipping a second reel to the bottom of the first reel should you encounter a current sheer (currents moving in opposite directions in the same column of water).  This will cause the bag to travel horizontally and if your deco is long and begins deep you will most likely be dragged past your first stops if you do not do this.

Bags are always deployed from the wreck, no matter how deep. If you wait until you are shallow to deploy the bag you will most likely be lost. Currents in South Florida are quite severe and it is not unusual to drift 5-6 miles or more on a long deco.

Whatever emergency signal protocol is decided on, communicating it with the Captain and crew is paramount. Every team and boat will usually have their own protocols.  If you don’t communicate which one you intend to use the probability of a problem increases exponentially.  Never assume the crew will recognize a certain color or type of bag as an emergency signal.  It and any associated nuances should be discussed in detail before the dive.  The crew should have a clear picture of what to look for.  My preference is to send up a second bag on an already deployed reel and bag combination.  Do this by clipping the second bag’s bolt snap to the already deployed line and putting air in it.  Be sure to pull the line taut and the bag will rise to the surface easily and quickly.  There can be no mistaking this signal which is why I prefer it.

Re spools – they are great navigational tools but they are not appropriate for deploying a lift bag from depth. They are the wrong tool for the job. I’m not saying it can’t be done, but a simple reel is much easier to manage.

I clip my reels and bags to a D-Ring that is easily accessible and hopefully minimizes their impact on trim. Wherever stowed, I need to be able to access it easily and quickly. I also try to anticipate my needs.  If deep and in a raging current I want to have the second reel ready to attach to the first in the event a current sheer drags the bag or SMB horizontally.  I always deploy with my back to the current and in a position that will clear the wrecks superstructure.

I also use the bag / SMB as a tool to take me to my first stop as opposed to allowing the reel to play out and then begin the task of unnecessarily reeling in line. To do this I deploy the bag and when it gains velocity I lock up the spinning reel with my hand over the spool (never use the lock down screw for this – it needs to be very easy to release). I have the reel in one hand and my inflator in the other and when I approach my first stop I release the reel and dump gas. I can stop immediately using this method.

Deployment of a lift bag or SMB on a deep dive can be extremely hazardous if done incorrectly.  While there are several acceptable methods what is most critical is to minimize the risk of entanglement.  First, your back must be to the current so any potentially loose line will drift away from you.  If you are not sure which way that might be, release a few feet of line and see which way it drifts.  Turn so it drifts away from you and your back will be to the current.

When you are ready to deploy the bag it is best to be horizontal.  This minimizes the risk of entanglement because there is a smaller area exposed to the ascending line.  My preferred method is to get horizontal and secure the bag to the reel.  Then unlock the reel and let the bag drop 5-10 feet below you.  Next lock the reel and drop it while bringing the bag back up.  You are now horizontal with the bag  in hand and in front of you and with the reel dangling a few feet below.  Holding the bag away from your body put just enough gas in it to make it buoyant.  You should be able to hold it in place similar to a kids helium balloon if necessary.  When ready, release the bag while “OK’ing” the line and when the reel rises to your hand release the spool locking bolt and deploy as you would normally.  This method minimizes the risk of entanglement.

If you have a buddy with you the 2 man method is safest.  The man with the bag puts his back to the current and gets to the side and a bit above the man with the reel.  When ready, the man with the reel signals the man with the bag to deploy it.  When he does so the bag will rise above and away from both divers ensuring there will be no entanglements.

When working a reel anywhere, but especially in high flow situations it is very important to keep the line taut at all times.  If you allow it to go limp it can easily wrap itself around you, a potentially dangerous and at the very least embarrassing situation.

Lift bag skills are very important to the technical diver.  Often, divers are shy about deploying them because they don’t do it enough.  Don’t be.  That bag can save your life not only as a marker buoy but as an alternate form of flotation.  BC’s and Wings can fail.  Dry suits can blow gas out the neck seal and can be unwieldy as your only form of flotation.  A diver skilled in the use of a lift bag can get himself safely to the surface using it alone or in combination with a failed Wing / BC or dry suit.  Consider it your “ace in the hole” or a get out of jail free card.

Why Manual? The Debate Goes On

“Regardless of where the ‘parachute’ is set, nobody has yet explained why this is anything other than a daft idea.”

The above quote was taken from a recent discussion on an internet dive forum about gradient factors.  As per the norm, it eventually morphed into a sub-discussion about about the benefits (or lack thereof) of diving an ECCR (Electronic Closed Circuit Rebreather) manually.  I considered joining the fray but then thought better of it. Having wasted time discussing topics with people who don’t want to hear what you have to say, I decided it would be more productive to write an article expressing my views.

For me … the concept of using the solenoid as a failsafe or parachute is for the express purpose of developing both muscle memory and an internal clock in your head.  This will eventually enable you to intuitively know when the solenoid is supposed to fire.  Contrary to the opinions of some, it is NOT because anyone believes the electronics are unreliable.

When I dive I often like to use a controller set point of 1.0 and maintain a 1.2 or 1.3 manually.  When I hear the solenoid fire I view it as the machine telling me “Hey, dummy!  Pay attention!”  To make it interesting I try to make a game out of it.  I like to see how long I can go without the solenoid firing.  In the spirit of “every dive is a training dive” I use this as a learning / teaching tool.  If the machine fails I will (hopefully) easily catch it because I have trained myself to be acutely aware of what is going on with my ppO2, all by making it a game rather than a “chore”.  Of course, when I have a “busy” dive, I use the solenoid and fully appreciate the convenience it brings to the table.  Interestingly, I also find that subconsciously I know about when I should hear it fire and have found myself reaching for the manual add O2 button at the same time the solenoid is doing its job.  This kind of validates the main purpose of the exercise.

For a seriously deep dive I favor not using the solenoid at depth.  My preference is to dial it back to a safe level that is well below the desired set point.  The idea is that it is far less likely to stick in the open position if it is not opening and closing.  Also, remembering that it is not necessary to add O2 on descent, if you use the correct diluent, you should be close to your desired set point once you reach target depth.  My rationale is that a stuck open solenoid at say 5 – 600 feet is quite serious and its risk should be minimized.  I mitigate that risk by using the proper diluent gas for the dive; one that gives me an acceptable ppO2 at depth, manually tweaking it when necessary.  I use the solenoid on ascent where a stuck open failure is not quite so serious and much easier to manage.

To those whose opinions differ and believe utilizing the electronics is the preferred way to dive I say fine.  I agree that the human hand on a button is no match for the precision with which todays modern controllers hold set point.  I just prefer to retain as much control over the unit as is reasonably possible.  If I were to buy a Ferrari or a Lamborghini I would want a manual transmission even if an automatic was available because I want to DRIVE the car, not the other way around.  In that same spirit, I want to DIVE my rebreather.