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DDS Diver Grace doing a CCR Trimix Dive in Bon Echo Park

When Should You Get a Rebreather

When Should You Get a Rebreather
by
Matthew Mandziuk

Lately people have been asking us about rebreathers and when they should consider going that direction…So I figured “When Should You Get a Rebreather” would be a fun topic to write about.

Rebreathers are a simple concept.  A rebreather is in essence like breathing from a “sealed bag” is filled with a breathable gas mixture.  As you breath each breath, you deplete the oxygen in the “bag” through the process of metabolizing the oxygen and putting back in the lung exhaled breath with a lesser partial pressure of oxygen until the “sealed bag” or “lung” would go hypoxic (think of breathing in and out of a paper bag as a concept), meaning not enough oxygen is in the gas you’re breathing to sustain life.

You would have to replace the depleted oxygen with more oxygen, but in addition to this, you’ll also have make sure that carbon dioxide is also being absorbed/eliminated from your rebreathed gas, so we need to “scrub” the CO2 out with a CO2 “scrubber”….Sound simple?  It is overall.

Below we will discuss who should dive a rebreather, the different basic designs and features, key elements, dive planning and more.

There are 2 types of rebreather concepts.  Semi-Closed and Fully Closed.

fathom rebreather rigged up as the tech version with faber LP50 tanks, Lola valves, atomic regulators, custom black camo halcyon evolve jj wing with maroon center, spg on left hip with diluent injection through the left hip d-ring
Fathom MK2.5 CCR Tech Rigged

Semi-Closed is less popular for the vast majority because it’s a glorified gas extender with an efficiency ranging from 8:1 to as high as 10:1 efficiency.  They can use the same lung that a life-support patient breaths from which passively allows excess gas to vent from the bottom of the unit while the lung is refilled.

The Passive Semi-Closed Rebreather is very popular for depths where open and closed circuit scuba are less reliable.  PSCR Divers often use larger cylinders.

Fully Closed Rebreathers utilize smaller tanks, a greater degree of efficiency as high as 40:1 that of open circuit because when the efficiency is met, the diver recycles the entire exhaled breath and only has to inject the oxygen when the PO2 drops.  They can be more complicated but are more popular at the time of this writing

Rebreathers ARE NOT For Everyone

With the Cost of Helium increasing, more and more people are looking to breath more efficiently, however, diving a rebreather requires a higher level of awareness, technique, buoyancy, trim, knowledge of the machine and what can go wrong and how to troubleshoot problems.

It’s only a matter of time until Rebreathers become more common practice to the masses, however, now is not the time for most people because they don’t have the training or the experience.

Helium keeps going up and up, but that doesn’t mean unqualified Divers should be jumping in blind and bypassing all the experience and fun that is had learning and logging the experience dives that makes a person a better Diver.

Here are illustrations of a basic rebreather design and semi-closed rebreather design courtesy of the NAUI Rebreather Instructor Guide.

SCR Rebreather
SCR Rebreather
Closed Circuit Rebreather Diagram
CCR

Types of Closed Circuit Rebreathers

Choosing the right rebreather for the individual is key.  There is no perfect one rebreather of everybody.

Automatic: Some Divers prefer an automatic rebreather than much like a dive computer, runs the dive for them setting a constant PO2 (oxygen set point) for them on descent and maximum depth injecting oxygen using a solenoid .

Unless the Diver remembers to set the computer to a lower set point on ascent, this can cause problems for the Diver as the unit will continue to inject oxygen as the depth reduces because as the diver goes shallower, the Po2 will drop, so if the Diver ascends from depth at a PO2 set point of 1.2ata the rebreather will try to keep filling the lung with oxygen, whereas, the diver needs to set their set point lower to 0.6ata and they can ascend without worrying about an out of control ascent and manually adjust their set point to their desired level.

Continuous Mass Flow and Needle Valves: Some rebreathers use what’s called a needle valve which uses a “Mass Flow” orifice on the regulator of the O2 tank. The Diver can set their oxygen set point based on their metabolic oxygen rate by adjusting the Needle Valve.

The needle valve will gently flow oxygen into the counterlung so if the diver becomes task loaded and isn’t watching their Po2 (which should never happen), they needle valve will prevent the Diver from going Hypoxic.

You’ll find the Mass Flow a great option which is why the original KISS Rebreathers are still one of the simplest designs, while the updated Needle Valve design of Fathom CCR  is becoming so popular.

The Continuous Mass Flow system is limited by depth.  The intermediate pressure of the regulator first stage can reach the same as ambient pressure meaning an intermediate pressure in the first stage of 10BAR/145psi will not put out any more gas past 81msw/260fsw.

The Fathom System corrects the by modifying a diaphragm sealed first stage with a stronger spring which allows for safe boosting of the intermediate pressure up to as high as 205psi/14BAR which is capable of diving to depths of 120msw/395fsw.  The pressure can also be increased up to 290psi/20bar for up to 585fsw or 177msw!!!

Excerp from the Fathom Page: “Smaller fixed-orifices can also be used for deeper depths with higher intermediate pressures but the risk of a blockage is increased and the options are limited by orifice availability. A fixed-orifice requires that the first stage intermediate pressure be adjusted to achieve a flow rate that corresponds to the diver’s metabolic needs, typically around 0.6 to 0.8 L/min. Conversely, the needle valve allows the first-stage intermediate pressure to be set to any pressure since the needle valve handles the flow adjustments. More importantly, the needle valve minimizes the risk of a blockage from debris since it can be opened up to allow small particles to pass. The oxygen MAV, which contains the needle-valve, is ported directly into the exhaust side of the head so oxygen must travel through the scrubber and mix with loop gas before reaching the diver.

1 (145 psi/14.7 psi/ata – 2 ata) x 33 fsw/ata = 260 fsw  (Note: always subtract 2 ata when calculating the maximum operational depth of a CMF system.)”

Diving the Bell Island Mine with Explorer and Rebreather Instructor Matt Mandziuk

Manual CCR: Manual Rebreathers are simple, easy to use, but require more attention to the instrumentation and require the operator to constantly inject oxygen based on their needs depressing an oxygen injection button allowing the Diver to adjust the oxygen as slowly or quickly as needed, in a similar fashion to how a diver would inflate their bcd.

When Diving a Manual CCR, the Diver will have to remember to monitor their Po2 and maintain the desired set point.

One of the more fun skills is “Volume Drop” which the CCR Diver will do in their initial training course to see how long it can take their mix to go near hypoxic from their targeted set point.

Keeping a consistent set point that mirrors a backup computer if there isn’t a second computer handset or NERD on the unit is a desired option.

Being diligent with keeping the oxygen level consistent is a must.

Simplicity and Reliability Should Favour Bells and Whistles

The more high tech of a rebreather, the more complacent some Divers get.  Whether you’re flying an automatic or manual system you should always be aware of your set point and Do Your Pre-Dive Checklist!

A Rebreather is a very Serious Piece of Equipment.

PSCR Rebreather
Semi Closed Rebreather Rigged and Ready to Dive with double 80’s in Mexico

A rebreather is essentially a nitrox or trimix gas mixing system that is designed to deliver a constant oxygen set point that acts as a gas extender to you diving more efficient.

With each exhaled breath you make on open circuit scuba, there is no way to get that exhaled gas back.

A rebreather recycles your exhaled air, which is typically 5-6% less oxygen than you inhaled.

When you exhale into a rebreather, you’re exhaling into a scrubber canister, which is essentially a “filter cartridge” that is filled with a carbon dioxide absorbent, a granual that traps the CO2 on granules that resemble kitty litter called Soda lime, which is used to remove CO2 from breathing gases to prevent CO2 retention and CO2 Poisoning.

The filtered gas enters a counterlung that allows you re-breath this recycled gas and as it continues to be re-breathed, oxygen has to be added on occasion to prevent hypoxia (not enough oxygen)….Some have said that a rebreather is “essentially slowly trying to kill you, so maintaining the oxygen levels is essential.”

With each breath in we drop our oxygen PO2 so as the levels drop, we need to add oxygen to “bump” up the levels or the oxygen percentage you’re breathing can go hypoxic meaning you don’t have enough oxygen to sustain life and can go unconscious and die.

White Arrow Axial Rebreather Scrubber Canister
White Arrow Axial Rebreather Scrubber
fathom rebreather scrubber regular and large size canisters
Fathom Radial Rebreather Scrubber by Golem Gear

Think of the Scrubber and counterlung as your cardiovascular system.

Radial vs Axial Scrubber

Radial Scrubber allows the gas to pass through he canister body and provides a lower work of breathing, but is more difficult to pack than Axial Scrubber canister.

As the Co2 Absorbent becomes wet through moisture/condensation, the absorbent can clump, which can make it more difficult for the gas to pass through it, thus increasing the work of breathing.

Axial scrubber size/length needs to be long enough to prevent channelling of gas and short enough to keep the work of breathing low enough.  A longer Axial scrubber will increase work of breathing.

For longer dives, a longer radial canister is much preferred as the work of breathing remains excellent on most designs.

There are also pre-packed scrubber cartridges available for some models of rebreather for the Diver who doesn’t want the responsibility or liability of packing a scrubber canister.  These are more costly, but effective.

Rebreather Fatalities are (approximately) 10 Times More Common than Open Circuit Scuba Fatalities

Diving a Rebreather is very different than diving traditional Scuba. You can’t control buoyancy the same way and they don’t deliver gas the same way. Some even have a very complicated bunch of electronics or bulky, dangling bits everywhere and a huge, bulky counterlung.

Many CCR Divers can’t do a “try dive” on the unit they think they want to buy, so unfortunately, we see many people making Very Poor Choices in their Selection.

Your best rebreather is ultimately the one you think you want, but honestly, the simplest, most reliable and mores streamlined rebreather is the one for you.

Avoid Bells and Whistle’s, and run the unit in “manual” mode instead of an automatic rebreather. Be In Control of Your Oxygen Levels, don’t trust the machine to do it all for you.

Get as polished as you can be and as experienced as you can be before you jump into a rebreather.

Who Should Dive a Rebreather?

If the CCR Diver is wanting to dive the a pair of shipwrecks within recreational limits and dump their scrubber after the dives are completed, the cost of absorbent and gas fills will cost more than Nitrox fill in doubles would, so unless that Diver is planning a longer than “No Stop” recreational time limits, or saving the absorbent after the days diving wraps up for another day of diving, there is no benefit to using a rebreather on those dives, other than practice.

Cave Divers can spend hours underwater just on a single dive, as can shipwreck divers, technical divers and research divers.  This is who a rebreather is best suited for.

NEVER ABANDON HOGARTHIAN/DIR/NTEC PRINCIPLES AND VALUES

Your rebreather configuration should be as streamlined as your doubles setup. Simple, Streamlined, Reliable, Familiar. Long hose is always off the right post, necklace (or BOV)  is always off the left post so they don’t roll closed when swimming through a restriction like a cave or shipwreck.

Most CCR Divers Don’t Mirror Open Circuit (Long Hose, Backmounted Diluent, SPG Left Hip, etc.), which makes the system more complicated and in a situation where task loading can become a problem, that’s never good.

200′ Trimix Dive with LP50’s, argon, Nitrox 50 and Oxygen

You should NEVER have to re-orient your stage bottle rigging (Always Valves Up Not Valves Down), positioning of your stages (Always Left Side). Running your valves “Valves Down” means your regulators are going to hit first when you do a stage drop.  Those diving in the Great Lakes also have to worry about Zebra Muscles slicing into your hoses.  It’s also easier to do a bubble check when your stage bottle valves are facing you.

Valves Up? or Valves Down on the Main Cylinders?  Diving 3L Cylinders you will trim out better with the valves upright like a standard K Valve, but the Valves Down is acceptable for some configurations too.

When Diving CCR with Aluminum 40’s or Faber LP50’s Valves Up is the Most Modern and Most Reasonable Option.

Diving PSCR Valves Up is the Only Option as well, since the cylinders are larger and your’re mirroring your Open Circuit Doubles Configuration.

You can also get a Sidemount Rebreather in PSCR or CCR.  Many of them do not breath well.

Remember the DIR…NTEC Principles are based around the concept of “Doing it Right”.

Not Enough Bailout Gas

One of the most common problems with rebreather divers is that they do not carry enough bailout gas!

You’ll sometimes see a cave or trimix diver doing a technical dive with 1-2 aluminum 40 cylinders.  In the unlikely event the diver is equipped with 3L (FX23 cubic foot) tanks, they should have a minimum of 2 stages.

Some Divers are also starting to use a Sidemount Rebreather as a bailout option.

Cave 1 Divers require a minimum of 140ft3 of bailout, while a Cave 2 level Diver requires a minimum volume of 225ft3.

This means that the average CCR Diver doing a cave dive with an aluminum 40 or a pair of 40’s isn’t carrying enough bailout in the event of a full failure of the unit where they’d be required to swim their bailout from the deepest point in the cave.

Even an AL80, AL40 and the 3L tanks aren’t generally enough for a cave 2 level dive, 2 80’s and bailout in fact aren’t either as that + the 3L cylinders is only 200ft3 of gas.

A recreational diver doing No Stop Diving can use a single AL40 from 40msw/130fsw.

A Technical Level 1 Diver 50msw/150fsw would require an AL80 and an AL40 to ensure they can hit the obligated deco stops ascending from max depth to first deco stops and in the second bottle should have at least a 50% nitrox mix to breath.

A Trimix 1 Diver (2 deco bottles in Open Circuit) generally certified to 60-72msw/200′-240′ should have at least 1 AL80 worth of bottom gas to ascent from max depth to first deco stops. A second AL80 to ascend form the 150-70′ range and then enough gas to get from 70′ to the surface.

A Trimix 2 Diver diving beyond 70msw/240fsw requires enough bailout to ascend from max depth to first deco stop, and then each additional phase of decompression.

A 91msw/300fsw would require roughly 150ft3 of open circuit bailout to the first required deco stop, which would be a trimix of a 21/35 or 23/25.  That would have to last the OC Diver up to the next required deco phase which should be 70′ and 50% Nitrox or a hyperopic trimix like 50/25, while others may opt for a 30/30 trimix breathed up to 20′ which would require yet another AL80 for the decompression phase.

You’ll start to see why the little 3L tanks aren’t enough for deeper trimix dives unless you split the bailout cylinders with your team member(s) to minimize what you’d have to carry.

For “Light” recreational dives, double Aluminum 40’s are a wonderful option offering 80 ft3 of bailout on the back.

SCR Rebreather
Try and Discover Rebreather Experience Today

A pair of Faber LP50’s filled “Florida Style” with a bottom trimix is more preferred for experienced rebreather divers.

For the Same Dive the LP50’s would bring the diver into the 55msw/180fsw range easily, switching to the 21/35, then up to the next deco phase at either 21msw/70fsw or 30msw/100′ and up to the 9m/20fsw phase where another AL80 of oxygen would be required.

It’s so important to plan ahead and plan for the worst, as you don’t want to be left with any surprises, and while a flooded rebreather or a total loss of your PO2 monitoring equipment is rare, which can happen, as can regulator failures, burst disc ruptures and more, but that’s why they call them a failure.  They’re unplanned.

Being Proficient in at minimum of 2 AL80 Stages is why I always encourage Divers to get to at least the Cave 2 or Trimix 1 level.

Maintenance

The pre-dive setup and post dive teardown of a rebreather could take far longer than the planned dive. Some units are easier to assemble and teardown than others, which should be a consideration.

Maintenance, pre-diving evaluation of all components which should be frequently inspected, as well as changing of the oxygen sensors every 6-12 months, servicing the regulators, fittings, o-rings, injection equipment should all be factored in.

If a leak is detected in the unit, it can cause more problems in the event of an emergency, as a flooded rebreather can have an unfavourable effect if the scrubber becomes wet, causing a “caustic cocktail” which can be an instant retching action that can cause the diver to go into a choking reflex as you ingest this corrosive, alkaline cocktail.  If a Diver tries to bail out to open circuit on a separate regulator they may involuntarily inhale more water, while simultaneously retching and possibly drown, this is where a Bail Out Valve or BOV is a very smart piece of equipment.  The BOV has a switch on the rebreather that allows you to open the breathing loop from closed circuit to an open circuit regulator.

The diver will then be able to breath or barf and breath through the second stage as they take sanity breaths for a couple of minutes.  Students are taught to purge empty the rebreather from water on their CCR Course.

Instead of a BOV, some rebreather divers use a DSV (Dive Surface Valve) to allow them to breath surface air topside.  This could be more risky in a caustic environment as the diver doesn’t have the ability to switch off closed circuit to open circuit in the even of a caustic cocktail, so utilizing a necklace under the chin reminiscent of how modern divers dive with a long hose/short hose configuration is the only reasonable option to get breathable gas if the unit is flooded.

People love the “Cool Factor”, but I wholeheartedly caution those who don’t cut it at the recreational or entry-level technical diving level to wake up and seriously ask yourself if you’re ready for all that CCR Diving entails.

A friend of ours who passed away recently ago used to say he never dove a rebreather because he had friends who were Doctors or Lawyers with more letters that were in front of their names who died on them.

Diving a Rebreather is more commonplace now, but unless the dives are super deep (below 150’ or more) or super long like those maybe a Marine Research Diver would be participating in, the reality is that diving Open Circuit is the more efficient choice for the average person.

Rebreathers require a much higher degree of attention, diligence and understanding of how the unit works.  The simpler the unit, the easier it may be to fix on the fly in the event of an equipment related issue.  You should always have multiple ways to receive breathable gas in an emergency, so always do your positive and negative checks, and test out the mushroom valves, regulators, fittings and practice drills regularly to keep your problem solving skills sharp.

Have a well stocked rebreather Save a Dive Kit of spare o-rings, regulator parts, breathing hoses and sensor(s).

Keeping Your Rebreather in “Dive Ready Condition” is a Must.

Pre-Dive Checks, Calibrating the Instruments, verifying flow rates (if applicable), packing your scrubber, then cleaning and disinfecting the unit is all part of rebreather diving.  Don’t be lazy and don’t be complacent.

Diving a Rebreather requires diligence and being familiar with all the inner workings of the unit.

Things to Consider.

Which Side does the oxygen inject in from?  Before or after the gas is analyzed? Does it have an ADV or a T-Block Piece?  How many different ways can you get breathable gas if you need it?  How does the unit breath flooded? Is the unit reliable?  Does it work in cold water or just warm water?  Is it lightweight for travel? Do you need to wear weights with it and how much?  Is the cost of the unit agreeable?

What are the entry requirements to training on a Rebreather?  Agencies who make it “too easy” don’t get the big picture.  Train harder, skill up and then go to a rebreather.  Don’t Take Short cuts.  See my previous blog post What’s The Hurry, What’s The Rush?.

You’re making a decision that can cost you over $10’000.00USD.  Do Your Research, but more importantly talk Us.  We do get Demo Units as well sometimes as trade-in’s.  We currently have a Sentinel CCR up for grabs.

Book a Try Dive with Us and see why our way is the best way.

All too often Divers go blindly into purchasing a rebreather and it’s not until they start putting the hours on their units do they realize they purchased the wrong one.

In Closing

Rebreathers are a lot of fun, as you can extend your dive times, see more creatures up close and more personal, it buys you time in an emergency if you’re trapped in a shipwreck or a cave to find an exit in the event of a collapse making them a safer choice for extreme cave diving and the deepest shipwreck diving.

50-100 Trimix Dives will more than pay for the rebreather and the training, so get your hours up in Open Circuit, get proficient with multiple stage bottles and let’s help you become a Rebreather Explorer.

Cave Explorer Matt Mandziuk retrieving line in a Florida Cave

Cave Diving – How I Got Into Diving Caves

Cave Diving – How I Got Into Diving Caves
by
Matthew Mandziuk

A lot of people ask me about Cave Diving – How I Got Into Diving Caves, and the truth is that it wasn’t on purpose. It was once upon a time when I was in Mexico doing some instructor updates for TDI. I’ve been a Technical Diving Instructor with them for over 20 years and I was looking for a trainer that could teach me more than the people I had met or worked with here in North America were able to offer. 

The Internet was relatively new to me…well most of us 20 years ago, but I had found a few trainers who kept coming up on WebCrawler and whatever other search engines I used…I think AOL. What drew me to Mexico was that the Instructor was seemingly offering something different in concept. His emails were more detailed even though English wasn’t his first language and the pictures looked like the gear was a lot tidier than my setup, which in those days was a very old school New Jersey Wreck Diving configuration, so I took a chance, hopped on a plane and went to Mexico.

We reconfigured my gear, as I was fascinated by how much cleaner and more streamlined the setup we were training new students on was and I embraced it all 100%.

It was knowledge that made sense and it made the diving so much more functional. (See the example of how my gear may or may not have looked at one point further down the post).

The Seasickness Day

One day we were out in the ocean boat diving in 14′ waves, when I got thrown from the boat by with all my gear on. Here was as good of a spot as any to drop on the wall, so we decided to drop right were I did and we conducted a nice 300’ trimix dive. As we entered the decompression phase of the dive shallower, the surge was very strong and I started getting a little queasy. After the stops were clear, we got tossed back onto the boat by the waves and we powered back to shore, I crawled tanks and all up the sandy beach on all 4’s and and kissed that unmoving ground. I likely even told it I loved it.

When my face wasn’t green anymore my Trainer started thinking about other less windy options and one of the ideas that popped into his mind was to do a deep sink hole, something I’d never seen before. I was in.

An Inland Road Trip

I remember the site well, Cenote Angelita. We drove into the jungle and parked a car, walked down a dirt pathway through the jungle of beautiful big trees, and we happened upon what looked like a tropical oasis in paradise. There were some tree roots we could use to walk down to the water way a little more safety and you could see down quite a ways into the water as the sun was peaking high in the sky just before noon.

When discussing the dive plan, we were briefed on the site and I got to discuss the dive with the dives I was diving with.  

We walked our decompression cylinders down to the water and tied a line off a series of strangler fig tree roots to clip the tanks to so they didn’t slip off the ledge down to over 200’.

We put our suits and double tanks on and on the surface we conducted our s-drill and bubble checks, clipped our additional cylinders on and away we went.

I remember looking into the air clear water and I could see all the way down to the bottom at 90’ where there was a hydrogen sulphur cloud and a beautiful reddish coloured rock in spots around the basin.

We explored the sink which was very reminiscent of Yoda’s planet Dagobah with the steam on the surface unearthing the trees sticking through the cloud, except this was now happening underwater and was one of the most mind-blowing and interesting things I’d ever seen in my life.

After taking in my new favourite site above the cloud, we decided to go in through the cloud. As we descended through the hydrogen sulphur cloud, I could actually taste through my regulator a flavour of sulphuric “rotten egg” which is a flavour everyone talks about. As I descended, I came into the darkness 40’ deeper and into a night dive like environment environment. HID Lights were just starting to come onto the market and it was my first time seeing a Halcyon 18w HID light in action. the blue light was so amazing. I was still using a 2 section car battery pack powering a 50w Halogen lamp, so my beam was yellow.

As I took the time to take in this new environment, I noticed a lot of branches, roots, a massive hour glass shaped debris cone, just like I’d read about in the many books I’d read on the Yucatan Peninsula and the water was even clearer below the cloud that above, which we could easily see the entire length of the basin above and below over 300’ of clarity on this day.

We kept following the debris cone downward towards the bottom which I could see getting closer and closer and we stopped at a cavern entrance with a beautiful speleothem hanging and all of the divers lit up the entrance with their high tech HID lights and my halogen lamp.

I Was Mind Blown…

I was mind blown and the entire dive had eclipsed all of my best dives in quality, uniqueness, clarity of water, cool things to see. I’d gone from never diving a sink hole to never seeing spelotherms, to being thrown into a new world of let’s discover what else is out here and a trip that was only supposed to be 1-2 weeks lasted a month, as I so excitedly and enthusiastically ascended after our decompression ended and smiling ear to ear they asked how I liked that site!? My reply was that it was the best dive ever. They later replied, if you like that we have some even bigger and better treats for you “Farmer” (in response to being seasick and kissing the sand the day before).

We did a second dive at Angelita was just as good, but a bit shallower as we broke 200′ of depth on the first dive. We had even more time to swim around and play in and out of the hydrogen sulphur cloud. It was very memorable.

An Example of full columns in a Cave
Photo by Matt Mandziuk

Upon feeling renewed and excited, we did a bunch of other fun dives in the area and all these big deep sink holes just made me more curious about what else was inside them.

One day I was asked to teach a decompression lecture for a bunch of cave students and was convinced to join on the open water skills dive on day 1 of these students working on their cavern skills. It was pitched to me that I could learn how to use a reel better and it would help make the best wreck diving class in the world.

The day we did the class, then we started working on dry land drills and having never actually been taught to run line and only reading from the old NSS-CDS and NACD cave books, I was excited to see how they did things, so I sat and watched and when the students were done, I too had a chance to play with the reels and line following and then I joined the group during the simulated air sharing while blindfolded and communicating during “touch contact” and I thoroughly enjoyed being blind and feeling the way the line in my hands moved left and right and up and down and how I could use the sense of touch to feel the plastic navigational markers as a way of knowing roughly where I was and what direction was out.

I was done all of my TDI Technical Instructor upgrades and lectures by this point and it was time to immerse myself into something new. Cavern Diver Training!

My first cavern training dive was in 20’ of open water at a cent called Car Wash. It was the most intense dive of my life because I was taking everything so seriously. We have a great Cave 2 Skills Video summary of some of the skills online if you’re interested CLICK HERE.

For those who know me, I’m a pretty OCD and very thorough person when it comes to diving. I’m hypersensitive to things and usually very very aware and I liked this because it was challenging me in a new and different way.

For those who have done a Wreck Penetration, Intro to Tech, Cavern or Cave class with me, I’m sure you’ll remember our 20-30’ dives too. The shallow skills development dives set the bar for things to come.

On my Cavern Training it was not different. We spent 1.5 hours in 20’ of water doing air shares with and without visibility, with and without a buddy, we simulated a lost guideline deploying a safety/backup reel and had to relocate the line, tie-off our safety line and follow the mainline until we found an arrow marking our exit and make an exit in the proper direction. 

DDS Divers Working on Line Handling and Awareness

Don’t Be Intimidated….

While many people find a dive like serious training dive to be intense or intimidating, it just made me want more. As a matter of fact, I took the next dives so seriously that it took me 20 minutes to even realize we were in a cavern because I was so focussed on the team, the communication, the line placements and etiquette, among the other pre-dive rituals we had ahead of the penetration into the cavern, that it felt more organized diving this way.

Once we tied into the main guideline I was able to break a sigh of relief that we found it and then I was able to stop and take it all in and this cavern became something that allowed my body and mind to slow down and take it all in as the stillness was enhanced, my breathing rate lower than the last 20 minutes had been and and I heard every heart beat, the sound of every breath flowing through my long hose towards my mouth and the lights all cascading a beautiful array of light patterns around this magical limestone paradise that were created millions of years ago.

As the divers began to signal the turn and exit and somehow one at a time had “equipment failures” with masks being removed, primary lights failing, people running out of gas, etc., I was watching and waiting for my time to exit and don’t really remember if/what the problems I would’ve encountered were, but again after sorting our gear back out when the scenarios were over, and our safety stop completed, we ascended into another monumental emotional diving bliss moment as we were all smiles and ready for the next challenges.

True Beauty…

The thing I loved most about the cave diving training were the beautiful caves we were training in. Seeing the ice-age looking formations that resemble the frozen icicles at a waterfall were hypnotic, as were the stalactites and full columns (once I was able to start enjoying them and paying less attention to the main guideline or the equipment that I knew was going to “fail” on the exit).

The skills that we had to do on the class were addictive and I even “died” on my lost line drill, which is a survival skill we do as we simulate losing the primary line and having to tie off our safety spool on a rock and blindly feeling for the primary line, hoping to hook it with our reel, or even our equipment or body. 

Skills that like were very sobering and they drove home the importance of paying attention to the team and surroundings at all times.

Learning to navigate a jump from one line to another cave line was another wonderful skill too, as it extended our range into these cave passages.

What I loved most about cave diving were the rules and how organized cave diving made me feel. I used to always say Wreck Divers used brawn and Cave Divers used brains. I’m a big advocate of diving smarter, not harder and Cave Diving was something that just made sense.

One of the most interesting aspects of the Mexican cave sites was the haloclines, a phenomena of waters of different density and temperature that can create a visual disturbance like mixing fresh water into a glass of saltwater resembling how a road shimmers in the hot summer heat.
Here you’ll notice the fresh water layer on top pushing, mixed water in the middle with the salt layer along the bottom.

Halocline Formation in a Mexican Cave During NAUI Cave 2 Class

A thermocline can get more brackish as your pass through the layer and it creates a greater mix of the salt and fresh water which can obscure view of the main guideline. Learning how to dive in Halocline Formation is important.

I learned some valuable lessons on the cave class as well and helped reconfigure my equipment, as I maybe had some “wreck diving” equipment, but not stuff gear that was as streamlined or as functional as the gear I ultimately embraced. Even a little think like the importance of a good pair of fins. I was an advocate of Mares Quattro’s for years, they were a fantastic pair of fins, but couldn’t figure out why I was having to kick to keep up with some of the other divers, given I was running 5 km’s/day, my friend Nick said to me straight up “it’s your fins. They’re too big, bulk and too inefficient”. I switched to Jet fins after I got to try them minutes later and never looked back.

Technical Diving at DDS Looked Reminiscent of this in the ’80’s and ’90’s. Lots of Gear and Task Loading with hoses ,tanks and gauges galore. Be Blessed You’re Learning the Right Way from Open Water On. This is Why Divers Come From All Over North America to Train with DDS.

The importance of the right equipment that suits the team’s mission and members best is very important and another favourite aspect of cave diving, as those team members can help with the line tension, retrieving arrows or cookies if asked, while having their gear rigged the same way in the same location always.

I remember on one of my first cave trips back to Mexico, I got to dive in one of my favourite Mexican cave, where we navigated through 3 different cave systems on 1 dive! Now of course each cave once it’s connected becomes part of the biggest cave system, but once upon a time they were 3 separate cave systems.

With proper dive planning, great gas consumption and the right safety gear, cave diving can be one of the most enjoyable and stimulating styles of diving ever.

Cave Diving is Not Dangerous. Breaking the rules, exceeding your level of training or experience is. The caves have been here for thousands and millions of years before divers started exploring them, they’re not the hazard, human error is.

In Cave Diving they use the expression “There are Old Cave Divers and There are Bold Cave Divers, but No Old Bold Cave Divers”. Having lost friends diving, it’s not fun, but at some point a rule was broken or a training limitation in the majority of the losses I’ve had to endure. Thinking of your friends and family first will act as insurance in wanting to return home safely, so that you don’t make unnecessary risks and you can keep your mind in the game.

Don’t Make Unnecessary Risks, it’s not worth it.

Diving at the Cenote El Pat (The Pit) a Deep Sinkhole with several
caves including one over 300′ deep we were diving in 2015.
Sun lit Jungle in Mexico on the trail topside to the world's largest underwater cave system. Sun light beaming like subtle lasers through the tree branches
The Sun light beams gently kiss the jungle as we make our way to the dive camp during the World’s Longest Underwater Cave Expedition in Mexico.

From Student to Teacher and Explorer


My cave training opened me up to a lot of amazing adventures, but the faster approach to the training was something I wasn’t as keen on. 

Many divers do a “zero to hero” cave class in certain places, it’s not to say it can’t be done, I did it, however, I was the only diver who knew how to frog kick, turn or fin backwards along with 2 students who’d done open water and advanced with the same instructor in a backplate/wing, but reverse frog wasn’t a required skill, nor was any previous experience in doubles and this is still the case in a lot of the more mainstream agencies.

I really felt like the other students could’ve benefited from a foundational skills class which really was just starting to become a thing 20 years ago. It was rare that divers would have learned the foundational skills and have proper horizontal trim. A Cave Instructor in Florida one day told me they are there to teach a student as much as they can in a week so they don’t die in a cave. Many have never worn doubles, been horizontal or frog kicked, so they do the best they can and they offer them the opportunity to re-take the course within 6-12 months of they practice and get the diving in, but what they really should do is teach them the foundational skills first and then focus on the cave skills/training next. On my cave class the others were new to all the gear and techniques and the open water dives we had done prior to the cavern dives were designed to try and teach them the basics of modern diving.

Cave diving was a lot more mental for me than physical, having to think of the procedures to lay a clothes pin (now we use cookies) or when to arrow and where, as I felt we were hit with a series of navigational decisions and there was a lot of additional gear thrown in like stages and so on.

Complex Navigation involves multiple navigational decisions, entering and exiting in different places, doing circuits, T’s, traverses, set-up and clean-up dives to execute the dive properly.

It wasn’t until I got out on my own exploring new caves, some known, some undiscovered cave sites that I started to gain or retain the knowledge and apply it. I had the skills, I could do the drills, but putting them to practical use was really what made me feel like a cave diver and made me a better diver.

Many divers are quite content just following the main guideline in and out, it’s enough for some people and definitely how you’d want to start off if you haven’t done a cave dive for a while. Ease yourself into the dives doing easy navigation or what I often call diving like a “pedestrian cave diver”, as the simple tour is a nice way to reacquaint yourself with the caves and running the reel and tying into the main guideline, you can assess the conditions and note the navigational jumps or places of interest for future dives.

When it came time for me to be teaching Cavern Diving, I had no interest in teaching Cave Diving. I had a few friends in Florida and Mexico who I’d send friends to dive with and train and that was good enough, but none of them really stuck with it and my local divers were getting more and more keen to go to see these amazing springs and cenotes.

All of the years I spent in Florida and Mexico started mounting up, I started seeing the masses who were cave diving and they were destroying the fragile stalactites in Mexico or breaking the limestone features of the Florida caves.  My favourite decoration in Ginnie Springs got destroyed last year I named it “Scooby Doo” Rock and one day someone decapitated Scooby likely with Doubles or a Run Away Scooter.

scooby-doo-rock
Scooby-Doo Rock before some ass decapitated him. Below is the after math of a beheaded Scooby

As more years went by, I started seeing people flutter kicking even in a no flow cave in Split Fins destroying the visibility, hand swimming and vertical diving habits, along with people pulling hard on the cave guidelines which should never be pulled or heaved on, and only held with caution letting the line slip effortlessly through your fist as you grip it in a touch contact hand position. Most divers didn’t know how to run line properly or at all, while some people were just running a single long line for 200’ into the caves and tying in to the main line with no regard for the other lines, divers, teams or anything.

During those days, it was our Divers loved ones who were telling me that they didn’t trust anyone random person to train their loved one’s and they insisted when their loved one was ready to step it to the next level that I’d be teaching them because if I was the only one they trusted 100%, which was flattering and I accepted eventually, which turned out to be a great move.

For the last 13 years I’ve enjoyed teaching caverns and caves, but finding a cave agency I could relate to and enjoy working with was a serious decision too. I teach for 5 different agencies, but what I wanted out of an agency was a brand that suggested divers get more diving in between each level, much like I had wished I’d done vs the “Zero to Hero” approach, so I looked at all the agency standards and all of the prerequisites that each agency insisted on and none of them were requiring experience in doubles, or a foundational skills series of skills such as fin kicks or horizontal trim, posture, buoyancy, which is why I looked at NAUI as my preferred Cave Diving agency. Seeing the NAUI Standards was a game changer for me.

NAUI allowed divers to dive a 1/3 of their gas in, out and exiting with 1/3 for reserve, while the majority were doing 1/6th in/out and 2/3 let for exit. No jumps off the mainline, or 1 at best. Being able to participate in multiple navigational decisions was also a great offering, as was the depth limit of 100’ max, no stop limits and insisting certified Cave 1 Divers had to log 20 logged Cave 1 dives after their certification above and beyond their cave training dives, obtain a technical certification before engaging in Cave 2.

There were gaps left in my basic cave training that I saw as a bit of a short coming with some of my dive buddies on my cave class not knowing how to fin using a modified frog kick, not having experience in doubles, trim, reel handling or line awareness prior to a NAUI Intro to Tech Class, no experience with stage/deco/ bottles prior to being handed them in a cavern/cave setting, lack of familiarity with canister lights and back-up lights, rescue diving scenarios dealing with oxygen toxicity and more.

Cave Diving has given our Canadian Divers another way to keep their skills sharp during the winter months and while most divers fade in and out of the recreational diving spectrum, I do find that those who commit to an Intro to Tech/Cavern course and actually pass, never stop diving, as Cave 1 and Cave 2 become their next classes and then as it’s been now 11 years later many of those Cave 1 and 2 divers are still joining us on our trips today.

Cave Diving offers some amazing exploration opportunities, some great personal challenges and some different opportunities for photography and other offerings too.

Cave Diving Explorers Nick and Matt Mandziuk assemble a decompression habitat on a deep cave diving expedition on Cenote el Pat in Mexico
Setting up a Decompression Habitat as part of a Trimix Cave Diving Expedition in Mexico

Avoid Rushing Through Basic Training and Into The “Trendy Toys”


There is never a substitute for experience.  Getting your skills in place and your hours up are the only true way to become a proficient diver.  It doesn’t happen easily or overnight.

Surround yourself with a group of Divers you can learn from.  We use a mentorship mentality that helps prepare new DDS Divers who aren’t trained in the DDS philosophies and we encourage our “home grown” Divers to stay as active as they can and to get involved as much as they can.

We are trend setters and people that were responsible for helping establish many of the protocols and procedures now taken as the bible of diving.

We innovated the most modern Sidemount Configuration before anyone started diving long hoses and embraced the most modern CCR Rebreather Configuration with back mounted diluent and off-board O2 before it was the norm.

A lot of divers jump into certain concepts because the wrong people are promoting the wrong progressions, maybe it’s because they themselves couldn’t dive the right gear for a physical reason like shoulder surgery or bad back, but nothing is better off a boat or driving a scooter than doubles.

Sidemount is a tool to get you into a place you can’t fit on singles or doubles or for shore diving. It is better suited after Cave 2 when the divers have extensive cave experience, the ability or desire to do tighter passages or “no mount” passages even. Sometimes caves are not accessible on doubles, so Sidemount is the Correct Tool Here.

There are many caves that are simply too tight to get into with doubles, so once you’re familiar with all the cave diving has to offer, Sidemount becomes another tool you can use for expeditions where you don’t know if the cave will widen or narrow further.

Sidemount is Not for Mixed Gas Diving and is a horrible choice when diving off a boat, especially if people are diving an unrefined Sidemount configuration which is typically what we see locally from most shops/instructors/divers who are not cave divers.

Sidemount is amazing in places where doubles aren’t available for rent, because you can maintain the redundancy.  Sometimes on shipwrecks or in caves, doubles don’t fit, so Sidemount is the tool of choice as well as for those who medically can’t reach their valves due to spinal or shoulder injuries (having an ill-fitting drysuit/undergarment are no excuse).

Rebreathers with small little 2-3 litre cylinders are also an issue we have. Most Cave Divers Do Not Carry Enough Bailout Gas. A Cave Level 1 Dive = 140ft3 bailout minimum. A Cave Level 2 Dive = 225ft3 bailout Minimum. This means said Cave Diver Needs to be excellent with multiple Decompression Cylinders. In NAUI Cave 2 Divers Learn to use 3-4 additional bottles plus doubles.

Get Good on Stages and Doubles Before Venturing into Sidemount or Rebreather. Once you’re proficient in those styles of diving You can do DPV Overhead/Cave Course which may be safer on a CCR for gas time and efficiency as you’re travelling further back in the cave, but you should always swim it first on Open Circuit First and See how many cylinders it takes for if/when the DPV fails and you may swim on out of it for real.

Taking the right training, buying the right gear, putting in the right amount of time practicing is essential for any divers success. Don’t Rush into caves, technical diving, rebreathers, sidemount diving.  Don’t Take Shortcuts in Your Training.

There are so many amazing dives sites at every depth level and ever training level you succeed at. There is always a next deepest, and next best as well.

Don’t even attempt to dive a Rebreather in a Cave unless you can hover motionless for 5 minutes no skulling horizontally, Knees Up, Fins Up, Arms Out in Trim and complete all the Foundational Skills with 2 Stage Bottles On. I say this because several people have been unsuccessful in Intro to Tech with us and jumped into a Rebreather and somehow got Normoxic Trimix certified standing and kneeling on the bottom, ascending holding the anchor mooring lines and flutter kicking silting out the ships just like their Instructors do.

Your Best Option for a Rebreather is Manual not electronic, so you’re in charge of your PO2 and can control your ascents easier without the set point screaming at your as the PO2 reduces on an automatic unit as it goes shallower while still trying to achieve it’s constant PO2. Run it at a .6 PO2 on ascent or manually. On Deep Cave Exploration a constant mass flow valve or needle valve modified from the original KISS Rebreather design is another great option.

Matt Cave Diving in Mexico with the White Arrow Explorer CCR Rebreather
Matt after a CCR Cave Dive in Taj Ma Ha Puerto Adventuras, MX

Cave Diving is for Divers Who Have Elite Skills and Discipline and a Desire to be the Most Polished Divers They Can Be.

Spending a lot of time in Florida, Dominican, Mexico and enjoying the recreational and exploration aspects of cave diving have been very fulfilling. I throughly enjoy expedition style diving, having been featured in magazines, YouTube videos, agency and personal expedition projects, including helping friends map the largest cave system in the world, just a couple of years ago, in a land so far away from this Covid pandemic are what keep me motivated and keep me going forward.

If Cave Diving Interests You, Do it Right. Take a Foundational Skills Class with DDS. If you’re curious about doubles, take a NAUI NTEC Doubles Workshop with Us, which will start you down the right path in equipment configuration basic foundational skills, while our NAUI Intro to Tech Course is the best Foundational Skills Class there is. It offers the right skills, information and adventure. Intro to Tech dovetails seamlessly into Cavern/Cave 1 too, so do it right and take the best training path. Don’t leave gaps in your training. Don’t Rush and Never Accept a Certification Card You Yourself Do Not Feel You Earned.

Our Cave, Wreck, Overhead and Technical Diving Courses are The Best in the industry! No other training agency offers a more through and complete Cave Diving Education and having such a small number of Cave Instructors keeps the quality high and the demand high.

Going from a Left Post Breathing Hose Stuffer to one of the First DIR Based Diving Instructors was the best move we made as a shop. Divers come for the best training offerings from around the Canada, the USA and other countries. I’ve been a Top Certifying Technical Diving Instructor over the last 20+ years and with your help will continue to offer the Highest Calibre of Recreational, Cave, Technical, Sidemount and Rebreather Training Possible.

Seeing the benefits of Divers learning in backplate/wing from open water, encouraging continuity in gear configuration, improving team diving communication and functionality and being able to up the game whenever possible are just some of the ways we’ve helped set the standard higher.

I am frequently involved in cave and shipwreck and other random dive expeditions of known and unknown entities and we continue to challenge myself and others through new environments and equipment whenever possible.

empty_spools_of_cave_line
There is nothing more fulfilling than running new line through a virgin cave emptying your spools Sistema Sac Aktun Expedition 2017

If You Want to Learn More About our Modern and Progressive Training Offerings, CLICK HERE

Thanks For Reading, Let’s Go Diving Soon!

Matt Mandziuk

Follow Me On Instagram @divesith and @dansdiveshop