Equipment
For the Masses not the Classes: Meet the Horizon
Semi-closed rebreathers (SCR) were the first purpose-built breathers for sport divers circa 1995—Thank you Draeger! But while tekkies clearly needed mixed-gas units, many believed that recreational divers would quickly follow suit with SCRs. Fewer bubbles, no troubles, right? Wrong, the migration never came, and the likes of Draeger, Fieno, and the Hollis Explorer ceased production. Now Italian scuba maker Mares is convinced that they’ve solved the problems with the Horizon—a smart eSCR designed for the masses. SSI Training Director Adam Wood explains.
by Adam Wood. Photos courtesy of Mares
In the past, Mares (pronounced Mahr-ehs) was never a brand you would have associated with technical diving. Their market was warm water, entry-level divers who preferred Italian style. Over the years, however, Mares has been a constant innovator, finding its own unique ways to solve problems where others just replicated past solutions. For example, when Apeks and others were adding crack adjustments to their second stages, Mares used their bypass tube system to deliver superior air flow.
Their high-fidelity testing and development approaches led Mares and Poseidon to become the only regulator suppliers to the US NAVY.
The Mares development team never stopped pushing the envelope, but these efforts magnified when Head Sports (Mares’ parent company) bought Scuba Schools International (SSI). Both Mares and SSI had long-standing beliefs that training developments and equipment innovations must go hand in hand.
SSI offers so much under one roof: swim school, lifeguarding, mermaid, snorkelling, freediving, scuba, XR, and CCR. Most of the Mares product lines complemented these beautifully, and as their educational opportunities changed, so did their catalogue. At that time, Mares wasn’t involved in technical diving, and they saw that it would take a team with knowledge and experience to bring the Mares level of innovation to technical diving.
Mares Goes Tech
Mares chose to build a line of technical products from the ground up. They started by training all internal staff—from workshop engineers to product designers and even management staff—in technical diving. This effort began with a three-week training event in Croatia, where they held meetings and delivered SSI technical instruction to help staff understand what technical diving was and what its participants wanted. For Mares, the entry into technical diving meant much more than just delivering a product line; in typical Italian fashion, they had to live it and feel the passion.
From there, the “XR” technical diving equipment line was born. Mares harnessed the potential of its mainstream scuba dealers who now had the option to teach entry level decompression programs through SSI. This project turned out to be a huge success, and what started out as a “soft tech” product line became a complete mainstream choice for technical divers.
The next logical step in the process was to use that same philosophy and dealer/training center base to increase their market share of rebreather training and unit sales. Mares considered purchasing two other mainstream rebreather manufacturers before reaching a deal with rEvo. There were many clear benefits to this choice, but perhaps the most clear was the chance to learn about the rebreather world from rEvo rebreather “guru” Paul Raymakers. Commitment to learning from subject matter experts and willingness to challenge their own ideas and norms is one extremely positive, if often frustrating, Mares trait.
The new project had straightforward goals: Create a rebreather that 99% of divers could (and would want to) use that was as simple to operate as single tank gear while offering the added benefits of longer bottom times and reduced gas use. The real kicker was to try, over time, to make it affordable!
This did not look easy, but Mares was thoughtful in its approach and looked to the past before starting development in earnest. Other brands had tried the “recreational rebreather” thing, and it wasn’t all sunshine and rainbows. Some would say the collapse of VR Technologies and the Hollis Explorer could be attributed to heavy investment in this market with little to no return.
The Mares rebreather had to tick a lot of boxes: It needed to be simple, lightweight, quick to assemble and disassemble, easy to train with, redundant and failsafe without adding complexity and, above all else, it needed to be cheap! One problem with the recreational rebreathers of the past was cost. After training investments, there was not a great difference between these recreational machines and full closed circuit rebreathers; this left the consumer thinking they paid a similar price for a less capable device.
Mares wanted the price to be comparable with OC equipment tailored to the same level of diving. For example, if you could do the same dives on a twinset and two deco stages, then the total cost of the rebreather should be comparable. To keep costs down, mass production was the only option; until now, this was unheard of in rebreather manufacturing.
Another substantial hurdle was convincing current rebreather divers and instructors that this product was not for them and that it never would be. You will never find a reason to sell your JJ or AP and buy a Horizon. Current CCR divers should not try to compare features. The Horizon carves a totally new path that is unlike anything produced before; keep that in mind while we discuss its features in detail.
Let’s start this quite geeky tome with an introduction to some of the Horizon’s main components.
Gas Addition
Electronic Delivery Valve (EAV) – This is the solenoid that opens and closes to allow supply gas to enter the loop. However, unlike a normal CCR solenoid, this one is normally open and current must be applied to close the valve. When in its open state, the flow rate is 25 L/min. This can be reduced to zero by applying current, or opening and closing the valve as required to achieve any flow rate in the range.
Constant Volumetric Flow (CVF) Orifice – Like the constant mass flow (CMF) valve in an mCCR or hybrid CCR, the CVF enables gas to flow at a fixed rate via a fixed orifice whenever the connected cylinder is open. In the Horizon, this is set to 5 L/min. The internal pressure (IP) of the Mares regulators used in the Horizon is not fixed like some mCCRS and will increase as depth increases; as such, the mass flow rate will also increase slightly.
The formula for this is:
Adjusted Flow rate = (IP at depth / IP at the surface) * Flow rate
Automatic Delivery Valve (ADV) – Mounted in the top scrubber compartment, the ADV is essentially a second stage regulator that delivers supply gas when loop volume is low enough to activate the diaphragm.
All three of these gas addition features are supplied from the same gas block. It is important to know that all hoses and gas connections are connected together in one system and are two-way. There are two (double end sealed) quick gas connectors (QGC) for gas on the Horizon: one on the left for bottom gas, and one on the right for decompression gas. The bottom gas regulator has an IP of 10 bar/145 psi and the decompression gas regulator has an IP of 12 bar/174 psi.
When only the bottom gas cylinder valve is open, all systems, ADV, EAV, CVF, BOV, wing, drysuit and second stages on both cylinders are supplied by bottom gas. When the decompression gas cylinder valve is open, all systems including both second stages on the cylinders will be supplied by decompression gas—even when the bottom gas cylinder valve is still open
This makes gas switching on the Horizon super simple. Confirm personally and with the team that you are above MOD and open the decompression gas cylinder valve, tell the onboard computer that you have switched gas, and that’s it. The decompression gas regulator IP overrides the bottom gas regulator IP, and all systems are now supplied from decompression gas. The computer performs some small tasks in the background to ensure that you’re on the right gas, but more on that later.
A Semiclosed Rebreather
So we have the basics of a two-gas semi-closed rebreather (SCR) at this point. How do we know what we are breathing and that it is a safe gas? There are some basics to understand. If we add nitrox to an SCR, we will be breathing a gas containing less oxygen than that we supplied it with—how much less? Well, that depends on your metabolism (VO2) measured in liters of oxygen per minute.
A diver at rest might metabolise between 0.6 and 0.8 liters of oxygen per minute at continuous hard work (e.g., swimming in an extremely heavy current). That might rise to 2 L/min, and the most you are likely to see is 3 L/min; however, this rate isn’t sustainable long-term.
It is important to remember that oxygen consumption is affected by changes in work rate and metabolism, not changes in depth. So the same effort at 10 m uses the same amount of oxygen as it does at 40 m. And the Horizon SCR can supply a maximum of 30 L of supply gas per minute: 25 L from the EAV and 5 L from the CVF.
To work out what you are breathing on the Horizon (Loop fraction of oxygen, orFO2), remember that whatever gas is vented from the OPV is the same gas that is entering your body since you’re breathing from the same bag:
Loop FO2 = [(Flow Rate * Cylinder FO2) – VO2] / (Flow Rate – VO2)
For the Horizon, the minimum oxygen content for supply gas is 30%, and the maximum is 100%. The upper limit is clear, but where does the 30% lower limit come from?
If we rearrange the formula above, we can see that a diver with 30% Nitrox as a supply gas and a metabolic rate of 3 L/min requires a flow rate of 30 L/min to sustain a loop FO2 of 22%:
Flow Rate = VO2 * ( 1 – Loop FO2) / (Cylinder FO2 – Loop FO2)
Flow Rate = 3 * (1 – 0.22) / (0.30 – 0.22)
Flow Rate = 3 * 0.78 / 0.08
Flow Rate = 3 * 9.75
Flow Rate = 29.25 ≈ 30 L/min
In the table below, you can see what happens with various flow rates and VO2s when using a 30% supply gas:
The next table shows what happens if we were to supply the SCR with air even with a relatively low metabolic oxygen consumption of 0.8 L/min:
Even for very high flow rates, the gas would be hypoxic (less than 21%). At a moderate or high work rate, the loop FO2 would be far too low. For safety reasons and CE regulations, the lowest acceptable fraction of oxygen in the SCR at the surface is 21%. This is why air cannot be a supply gas and the minimum oxygen content is set to 30%.
A return to the FO2 formula confirms this:
Loop FO2 = [(Flow Rate * Cylinder FO2) – VO2] / (Flow Rate – VO2)
Loop FO2 = [(30 * .21) – 3 / (30 – 3)
Loop FO2 = (6.3 – 3) / 27
Loop FO2 = 3.3 / 27
Loop FO2 = 0.12
During the automated pre-dive sequence, the Horizon will analyse the FO2 of both the bottom and decompression gases to determine if they are in range, +/- 1% for bottom gas and +/-5% for decompression gas. The really cool thing about this process is that it shows the FO2 it’s analysing as it goes, so you know if you put in the gases wrong or if you received the wrong gas from the fill station. This process does two things: It confirms calibration as the calibration process is done with air and ensures each regulator is fitted to the right cylinder of the correct gas.
Oxygen Measurement
Another neat feature is that the gas from the EAV is added directly to the cell face of one of the two oxygen cells. This means a periodic gas check procedure can take place to ensure the right tank is open, the cells are performing as expected, and the EAV is opening and closing. The Horizon is equipped with two galvanic oxygen sensors to monitor the gas in the loop. To aid simplicity of training and understanding for the diver, they are only ever displayed as loop “nitrox percentage (FO2) However, in the background, these cells work like any other rebreather, turning oxygen into voltage which can be converted into FO2.
There is one “T” (test) sensor and one “F” (fraction) sensor. The EAV adds gas directly to the test sensor every 5 minutes during the dive; this process confirms that the correct cylinder is open, and it uses a known gas (analysed while the machine was at the surface) at a known depth (taken from depth sensor) to determine if the right FO2 is generated. This first test confirms the T sensor is accurate. The next part of the test requires 20 to 30 seconds of breathing (something we hope the diver is still doing) to mix the gas in the chamber. The two cells are then compared, and any variation will show an error and ask the diver to either end the dive or bail out.
In almost all instances, any error or failure of the Horizon will lead to a failsafe mode scenario where the EAVs power will be cut and will flow gas at its maximum rate of 25 L/min adding to the 5 L/min from the CVF orifice. No matter how hard the diver works, the machine will now maintain a breathable loop. The gas consumption will rise significantly and the diver will be prompted to ascend or bail out.
Calibration is often a pain point for CCR divers, and poor calibration can lead to serious consequences. Some machines have automated processes, some are manual, some require additional calibration kits, and some do not; however, it is always critical to perform the steps exactly as directed to get a quality calibration.
The Horizon simplifies calibration by mechanically integrating the process. The machine will periodically suggest that divers calibrate and will prompt them if the calibration falls out of range. However, it is good practice to calibrate daily. First, the diver selects “Oxygen Sensor Calibration” from the menu on the DC (Dive Controller). The unit prompts the diver to remove the bottom scrubber and remove the cell tray. The calibration confirmation button is located under that cell try so the diver must expose the cells to air or the button cannot be pressed. Like any other rebreather, voltages are stored and values are set.
How Efficient is the Horizon?
Well that depends a little on the setpoint and how hard you’re working, but in practice it is very efficient indeed. With the right choice of gas and setpoint, you can achieve very low flow rates with gentle finning. The setpoint is the FO2 in the loop you would like the Horizon to maintain, obviously this can never be higher than the FO2 of the supply gas and, as a fixed rule, it can never be less than 23%.
I recently completed a dive in the Maldives: I used a 30% bottom gas with a bottom setpoint of 23% and a 70% decompression gas with a setpoint of 63%. Max depth was 40 m/130 ft, and dive time was two hours. The bottom gas flow rate was calculated at 8 L/min and the decompression gas flow rate was calculated at 3.6 L/min. I used 60 bar from my S80 of bottom gas and 30 bar from S80 of decompression gas.
You will note an apparent mistake in the above paragraph: How could I have a flow rate of 3.6 L/min when the minimum the Horizon can supply even with the EAV shut is 5 L/min? That’s the difference between my calculated flow rate and real life. In reality, my VO2 was not high enough to metabolise the loop FO2 down to the 63% setpoint (3.6 L/min) as gas was flowing in at 5 L/min. I was actually breathing 65%, slightly higher than my planned setpoint. All the better for deco (i.e., there were higher oxygen levels). I did actually know that 5 L/min was the minimum during my gas usage plan, so took that into account.
CO2 Removal
The Horizon takes its scrubber design from arguably the best feature of its big sister, the rEvo. The dual scrubber design has many top features, including its low profile axial design: once they’re on the diver’s back, the two scrubbers are vertical. This helps the material to settle without the potential for channelling and distributes the weight evenly and high on the divers back.
Another great feature is the redundancy of two scrubbers. Even with a breakthrough in one scrubber, the second is there to act as a backup. The Horizon uses two 1 kg Sofnolime 797 scrubbers good for:
> 70 minutes under CE conditions for PCO2 = 5 mbar
(CO2 1. Ll/min, RMV 40 L/min, 2 L tidal volume, 40 m, 4º C)
> 80 minutes under CE conditions for PCO2 = 10 mbar
(CO2 1.6 L/min, RMV 40 L/min, 2 L tidal volume, 40 m, 4º C)
However, we all know CE conditions are not always realistic, so Mares conducted real world tests using the CE apparatus to determine the duration of the absorbent in the Horizon. The test revealed scrubber duration was:
> 180 minutes for PCO2 = 5 mbar
(CO2 1.0 L/min, RMV 22.5 L/min, 1.5 L tidal volume, 40 m, 15º C)
For scrubber durations, the diver has two options based on temperature. If the temperature is less than 15º C, then change both scrubbers after 180 min. If the temperature is greater than 15º C, then change only one scrubber per the scrubber replacement cycle. As the top scrubber is used first in warm water, move the unused bottom scrubber to the top scrubber position, emptying and refilling the now-new bottom scrubber.
As an additional safety feature, the Horizon tracks the scrubber usage in a unique way, using a process adapted (and simplified) from the rEvo. By telling the Horizon the weight and sex of the diver, it can estimate the CO2 produced by knowing the quantity of oxygen used. As the machine knows the cylinder FO2, the flow rate, and the loop FO2, it can easily determine how much oxygen was metabolised. Oxygen usage is directly proportional to the amount of CO2 produced. The Horizon then uses this figure to provide an estimated remaining scrubber time. If the diver were to work harder (metabolise more oxygen), the remaining scrubber time would diminish. If the scrubber time reaches one hour remaining, a warning is issued. It then repeats at 45 min and 30 min. At zero minutes remaining, the Horizon will go to failsafe mode: opening the EVA, delivering the maximum 30 L/min, flushing the unit with fresh gas, and alerting the diver to bail out.
The Horizon Electronics
The rEvo is fitted with Shearwater Research electronics—these represent a significant portion of the production costs. It was not possible for the Horizon to utilise the same tech and remain within budget. Using their technical knowledge, experience, and growing expertise, Mares decided they could rise to the challenge and create their own controller. Bulhmann had started to be implemented in Mares recreational computers and, looking around the market, it was clear there were very few competitors to Shearwater. Again, after analysing the benefits and drawbacks of the Shearwater products, a Horizon controller needed to be simple to use, with high quality feel and screen layout. It was decided Mares needed to make their own controller.
E1, E2, and DC
Being a life support system, the Horizon needed to have redundant electronic systems to ensure that in the unlikely event of one system failure the other will ensure the power is cut to EAV. These redundant electronics are called E1 and E2 respectively and are located in the electronics module below the bottom scrubber. They are in constant communication with the dive controller (DC) located in the handset.
If either computer loses communication or detects an error, the machine activates the failsafe mode. Each electronic controller has its own battery: the DC battery is located in the handset and the E2 battery in the electronics compartment. The battery for E1 is conveniently located in the separate battery compartment for ease of access. This is basically a USB-C power pack that can be removed for charging away from the unit for instances like liveaboard diving or when it’s not practical to take your rebreather in the house.
Another cool part of that is you can carry spare E1 batteries in case of the “forgot to charge” scenario or when diving in remote locations. E2 and DC both draw their power from E1 and can go from flat to a state ready to dive (Charge state <30%) in only 30 minutes. If you can get the unit next to a power outlet, you can push charge to DC and E2 while E1 is connected to the unit. Normally this is handled by the auto charge sequence, but it can be overridden as required.
What Is It Like To Dive?
In short, super easy! The exhale resistance is very low and, when in trim, not even noticeable— the work of breathing is <2.75 J/L (joules per litre) with a 75 L RMV, 40 m, 4º C, and 2 kg of 797 Sofnolime. When I explain how it feels to dive, the best way to describe it is, “How you expected scuba to be”—right up until the instructor told you that you go up with inhalation and down with exhalation. You suddenly worked out for yourself buoyancy control is one of the finer points of OC diving.
Cross that with how you thought CCR diving would be… you do not go up or down on inhalation and exhalation! That is until you tried it for the first time and realised that even small changes in depth cause the loop to expand or contract rapidly, causing waves of buoyancy that come and go. On the Horizon, the loop is almost always full; even a moderately fast descent is often negated by the CVF and EAV so the ADV does not activate. There is no need to vent gas from the loop on ascent as excess loop volume just leaves via the OPV without any “full” feeling in the loop. You continue to breathe in and out while changing depth as required; when you reach your new depth, set the wing to achieve neutral buoyancy, and you will stay there. It really is as simple as that.
The user interface is intuitive and simple: current gas and setpoint selection at the bottom, current loop FO2 and remaining scrubber on the right. Current depth and dive time are nice and clear in large font at the top. The centre is reserved for NDL and deco stop depth, time, and TTS. Other info on CNS and O2 are available from the next page menu.
When in surface mode, the whole menu is visible so you can see which item will be selected next, a welcome feature for those used to Shearwater. Menu options show some exciting features still to be launched on the Horizon, including wireless gas integration, digital compass, Bluetooth connection for dive log download and update, plus predictive deco functions. At the time of writing, the menu options are gas settings, pre-jump check, sensor calibration, scrubber settings, gradient factors settings, and dive and DC settings (Brightness, PO2, alarms and warnings, etc.). The only selectable options in dive mode are switch to OC, change setpoint, or change gas; keeping this process simple makes the Horizon feel very familiar very quickly.
There are two fully integrated weight pockets, one on top and one on the bottom of the case. The top can hold 2.5 kg and the bottom 3 kg. As the scrubber is placed equally on the back and counter lungs run up each side, the trim is pretty much perfect right out of the box. The unit is very short and sits high on the back, so it’s fitted with an integrated buttplate that adds some rigidity and length to the unit to prevent back pain. When you tie this together with a nice loop bungee set of side mounted tanks, even the worst divers trim out super nicely. As the quick loop connectors come from the sides of the top case, you can extend your neck and head back fully without hitting anything, giving good forward visibility in zero trim.
The BOV is extremely lightweight and with silicone soft loop hoses feels nicely weighted in the mouth. The stainless steel hose weights (stolen directly from big sister rEvo) add a quality, premium feel to the unit. The BOV tested as well as the rEvo DSV in loop mode and as well as a Mares regulator in open circuit: something where many have tried but lots have failed. Clearly the best design for a regulator is not the best design for a DSV, so a compromise is always needed. Where is the compromise here? Well, it’s actually quite a neat one: They have had to position the OC exhale ports slightly vertically, meaning you must tilt your head back when you want to clear water from the BOV in OC mode. It’s not a deal breaker, but must be emphasised during training.
Training, Anyone?
Horizon training represents the perfect collaboration between agency and manufacturer. The steps for build up, failure drills, and general diving were in part specified by instructors and trainers at the point of design. This means the entry level, 30 m, No Decompression program (SCR Diving) takes only 4 dives and the 40 m Decompression (SCR Extended Range) program only 6 (performance is the only way to pass all SSI programs, so more dives may be required) The Instructor level is also easily attainable with 50 hour prerequisite and 3 day instructor program. As the machine and training are both produced “in house,” the manual relates directly to the machine, giving the best possible information transfer.
Divers wishing to cross over from CCR need only 1 confined water and 2 open water dives.
Currently only available through SSI, the prerequisites for training have been purposely made simple with 24 dives, Deep and Nitrox the only requirements for both the 30 m No Deco and 40 m Deco programs. You just need to decide how much time you have and if decompression diving is something you desire. (Upgrade at a later date is also possible by completing only the missing portions).
The academics are short and concise and do not include lots of complicated math as the diver does not need to know this information; these are delivered through SSI’s unique, high-quality digital training platform MySSI and include digital student and instructor manuals, review questions, checklists, skills videos and final exam. This tool allows more skill development time, increasing comfort and safety.
The Horizon is €3,999 and €4,500 for No Deco and Deco versions respectively. For your extra €500, you get a second decompression gas regulator with QGC to allow connection to the machine. Both units are capable of decompression and do not require software updates or unlock codes to upgrade. Training will cost between €700 and €1,000 depending on the instructor and course. So, for €5,500, a diver will be trained for accelerated decompression to 40 m with dive times up to 3 hours.
To get comparable training and the equipment on open circuit (twinset or sidemount fully equipped with stages to allow 3 hours diving and training, plus accelerated deco training) will be close to €4,000. Mares hopes that the success of the Horizon will allow further efficiencies in mass production allowing them to recoup the R&D cost sooner and then make the product even more affordable.
Post-Dive Debrief
What is it like to live with? Simple and easy! After diving, you remove the loop, back cover, two scrubber caps, and both scrubbers. The only part that cannot be flushed with fresh water and disinfectant is the cell tray that hangs neatly on the top scrubber lock. You can rinse the entire machine and be ready to start your build checklist in under 2 minutes. There are two OPV-style pull dumps at the bottom of both counterlungs; these are not used during diving at all and are there only to serve as a very efficient way of draining the cleaning fluid. The entire internal system is open to fresh air and you can see the insides of the counterlungs, so drying is much faster than other rebreathers.
Travelling with Horizon was a significant part of the design brief. At only 12 kg ready-to-travel and being very low profile, it can fit in the bottom of your dive bag comfortably. The loop separates and packs down to almost nothing, you must now put two regulators in, and you are ready to rock! Most of the time, for 1-week warm water diving, I fit all my dive equipment, clothing, and SCR in one suitcase under the 23 kg standard airline weight limit. It’s as simple as travelling with OC.
However, part of the Mares model is that you might not need to travel with your unit—in fact, you might not even own one. The Horizon is perfectly suited to the rental market. There are cost incentives in place for dive centres to have multiple units on the shelf ready for the travelling diver to roll up and take for a spin.
Ongoing costs are reduced as much as possible: every six months, you should change one oxygen sensor (€70) and annually service the regulators (€95 each). There is no annual routine maintenance for the Horizon itself until year five. There are very few O-rings in the system, and these are inspected every buildup so will be replaced as required making the unit service interval every 5 years! Using only 1 kg of lime for every 3 hours of diving in warm water, the machine is very efficient. I find that an 11.1 L of 30% (€8) will last 2 to 3 dives and 11.1 L of 70% (€25) will last 5 to 6 dives.
Because things do not always go as planned—and Mares understood that from the beginning—the design of the Horizon makes it very easy to remove almost any part to send for repair/service. The handset can be disconnected, the HUD can be replaced, and all batteries are replaceable and not potted. All these items need to be completed by a qualified engineer. Note that SSI ensures that all Horizon instructors are able to complete all unit maintenance and all Mares distributors can train Mares Horizon lab technicians.
I hope this article has shown some of the unique challenges Mares has overcome to make something very different from other options on today’s market. I urge you all to take a try-SCR experience and remember what it is that a recreational diver is really looking for. I believe the Horizon fits that purpose perfectly.
Adam Wood is an SSI International Training Director for recreational diving and SSI Extended Range Business and Training Director. He has written SSI’s market-leading range of digital programs for Open Circuit, Closed Circuit, and Overhead Environments. Adam also owns Divemaster Scuba, a full-service SSIDive Centre in the UK with two arms: one specialising in training recreational diving from Kids Scuba to Instructor and another focused on CCR. As a manufacturer-approved warranty and service centre for most major brands, they lead the way for equipment maintenance and repair. In addition to these roles, Adam is an active member of the dive community through various organisations and professional bodies, including as Rebreather Training Council representative for SSI, CCR ISO committee member, Santi brand ambassador, Reel Diving Ambassador, product design and tester for many manufacturers, BBC safety and support diver, and more. His passion is teaching and passing on knowledge and skills in recreational, technical, and rebreather diving at the instructor/instructor trainer level—to constantly raise the bar of scuba diving and challenge old perceptions and philosophies to make exceptional thinking divers and dive professionals.
Equipment
Configure Me This: The Annotated Sidemounter
We make a deep dive into the world of sidemount diving, and examine seven leading sidemount systems with guest editors Steve Davis and Stratis Kas.
This feature was created by Steve Davis, Stratis Kas and Michael Menduno. Introduction by Michael Menduno. Special thanks to Michael Thomas and brand representatives who helped us. Cover collage by SJ Alice Bennett with photos by Jason Brown of Bardo and Stratis Kas. Images by Stratis Kas unless noted.
🎶 Pre-dive Clicklist: Dave Brubeck – Take Five 🎶
At last, I am pleased to present InDEPTH’s long awaited sidemount edition, which has been in the works for over a year. The purpose of the issue is to celebrate the art and practice, as well as the equipment and culture of sidemount diving. Call it, “The Joys of Sidemount.” But whether you already follow the Bogarthian way, or simply regard it all as “widemount,” I promise you there is something for you in this issue.
The seed of an idea for a sidemount issue grew out of two things: First was the popularity and interest of our NOV 2021 feature that celebrated our innate gear headedness: “Annotated Tekkie,” which examined the question of what and how much kit is required to safely explore our underwater world. Diving is a technology-dependent activity to be sure.
Second, was, that we’ve been seeing tremendous growth and interest in sidemount diving we’ve been seeing. Like technical diving itself, what started in the cave community with small groups of experienced divers experimenting with DIY sidemount configs some three plus decades ago, has now blossomed into a mainstream, commercial tech diving activity in both cave and open water. Sidemount diving has now even spilled over into recreational diving—the configurational equivalent of recreational nitrox in the era of tech mixed gas diving.
One of the important inflection points was bringing sidemount diving out of the caves where the configuration was born, into open water. Sidemount pioneer Jeff Loflin was one of the individuals instrumental in bringing sidemount to recreational divers and the open water tech community. He explained it this way to me in our interview, “We were taking sidemount from the dark, and bringing it into the light.”
“We were taking sidemount from the dark, and bringing it into the light.”—Jeff Loflin
Interestingly, over the last decade, sidemount rebreathers, used as both a primary or a bailout, or both, have also gained significant traction driven by innovative vendors like KISS/XDEEP, SF2, Divesoft, and others. In fact, seven vendors are currently producing sidemount rebreathers. Note that we have also seen an increase in the number of chest-mounted units that can be integrated with sidemount systems. However, we decided to focus on open circuit sidemount for the purpose of this issue, andl address sidemount rebreathers at a later date.
Today, virtually all of the tech diving agencies offer open sidemount courses, with the possible exception of NAUITEC. For example, these range from “Intro to Tech” level sidemount courses, at RAID, which are aimed at getting divers into sidemount at the beginning of their tech journey. At the other end of the spectrum, Global Underwater Explorers (GUE) only offers a cave sidemount course to those who have completed GUE’s advanced cave training (Cave 2) and have at least 50 post-class cave dives.
Similarly, the majority of the major recreational agencies offer a recreational sidemount class for open water divers, including CMAS, NAUI, PADI, RAID, SDI, and SSI. Collectively, these agencies are issuing thousands of certifications a year.
So how big is sidemount diving? Good question, right?!?
How big is tech diving?!? We don’t really know. As an industry we suffer from a severe case of data insufficiency syndrome (DIS). [We can combat this—see our survey below!] However, in speaking with insiders involved in the sidemount business, some rough comparisons emerged.
Sidemount diving is likely bigger than rebreather diving, which according to estimates presented at Rebreather Forum 4 in April, likely represents about 15-20,000 divers globally. This seems like a plausible estimate given the significant cost difference, familiarity with the equipment, and perhaps greater accessibility to training and equipment with open circuit sidemount compared to rebreathers.
Another comparison: sidemount diving is likely bigger than cave diving! “Sidemount is not just used for cave diving anymore, but I would say that at least 80% of cave divers have at least tried, or have sidemount in their tool kit. Fifty percent or more dive it exclusively,” Dive Rite general manager Jared Hires explained. Add in tech sidemount diving in open water and wrecks, and the growing number recreational sidemount divers, and we are likely to arrive at what sidemount instructor Steve Davis of Sidemount Pros estimates as “Cave divers plus some.”
On the recreational side, a PADI exec told InDEPTH that PADI’s Sidemount Standard Specialty is now as popular as its Dry Suit Specialty, which is PADI’s third most popular Specialty Diver course, behind Enriched Air (Nitrox) Diver and Deep Diver, and ahead of Peak Performance Buoyancy. No drills on the knees, puhleez! I kid our friends at PADI.
Despite its growth and relative new-found prominence, sidemount still remains a kind of a best kept secret—the elephant in the restriction?—by which I mean many tekkies (including myself until recently) lack awareness and working knowledge of sidemount diving and may not have even tried it.
Not surprising divers being what they are, even among sidemount instructors and users, there’s a range of opinions on its use and application. On one hand, some view sidemount as a specific tool to be used exclusively for diminutive karst cave, on the other, many consider sidemount more of a platform choice. In fact, Davis, who you’ll hear more about in a minute, offered this question and assertion in our interview, Speaking Sidemount, and then went on and made his case:
“Is backmount the best tool for cave diving? No, it’s not. Sidemount is far and away the best tool for cave diving!”—Steve Davis
Certainly, many including GUE, would challenge this assertion. But on the other hand, who died and left legacy twinsets in charge? Jacques Cousteau? Is backmount intrinsically safer? Does it offer better performance? If so, please share the data with everyone. There is room for respectful debate. Of course, every platform has its strengths and weaknesses, and environmental conditions, and individual physical and preference differences play an important role in choosing the appropriate platform. However, because of the lack of awareness, knowledge, and direct experience in the overall diving community, the limitations of sidemount get exaggerated, and its application, perhaps, under appreciated.
“There’s absolutely nothing I can’t do in sidemount that you can do in doubles, and there are a shit ton of things that I can do in sidemount, that you can’t do in doubles.”—Edd Sorenson
As instructor trainer and cave rescuer Edd Sorenson explains in his Who’s Who interview, “People used to tell me all the time all the things I couldn’t do in sidemount, and still do. ‘You can’t dive off a boat, you can’t do this, you can’t do that, you can’t scooter, you can’t double stage, you can’t quad.’ I would tell everybody the same thing. There’s absolutely nothing I can’t do in sidemount that you can do in doubles, and there are a shit ton of things that I can do in sidemount, that you can’t do in doubles.” Note in his interview Sorenson recounts taking GUE founder and president Jarrod Jablonski for his first sidemount dive. A trust me dive with Edd? Trust me, you don’t want to miss it.
Not surprising, it seems that many, or most of the dedicated sidemount divers we spoke to for this issue (See: The Who’s Who of Sidemount Diving) offered some version of the following, and or, would likely agree with this meme:
Once You Go Side, You’ll Always Dive Wide.
Ha! I kid our backmount sisters and brothers. None the less, it’s clear that sidemount is here to stay!
Now I’m not a sidemount diver, yet (it’s on my list), and only one member of InDEPTH’s team dives sidemount, in caves. So, to help us with the issue, we enlisted the help of two sidemount experts to serve as guest editors. We reached out to New Zealand-based sidemount instructor, ambassador, and host of the “Speaking Sidemount” podcast Steve Davis, principal of Sidemount Pros. We also enlisted the help of Greek photographer/filmmaker, author, long time InDEPTH contributor, and cave and sidemount instructor, the inimitable Mr. Stratis Kas. Both of them helped with the selection people and sidemount systems we planned to highlight, and authored content for the issue.
Beginning with this lead story, “Configure Me This,” we explore seven recognized and storied sidemount systems, all of them a little different. Who knew there were that many? In contrast, it’s fair to say, backmount configs have generally become fairly standardized in the global tech community. Please note, that the majority of models are shown wearing their personalized branded gear not necessarily stock products.
Next, we offer the perspectives and stories of 34 leaders in the field, in a piece titled, “The Who’s Who of Sidemount Diving.” We also dive into the philosophy, culture, and practice of sidemount diving in “Speaking Sidemount” and “The What, Which and Why of Sidemount Diving’‘ with our guest editors.
In addition, we offer A Brief History Sidemount Diving with Lamar Hires, Bill Renaker and Patrick Widmann, and specifically the evolution of cold water vs warm water sidemount titled, “The Evolution of Sidemount System Design: Two Distinct Paths Shaped by Florida and Mexico,” by sidemount instructor and author Andy Davis. Finally, the issue wouldn’t be complete with a bit of DIY sidemount heresy from long time scuba engineer and troublemaker, Dave Mclean, call it Sidemount Heresy! Trust me, you’ll be better for the exposure!
Here then is InDEPTH’s celebration of sidemount diving and culture. We want to thank our forward thinking sponsors: DAN Europe, Dive Rite, Divesoft, Fourth Element, Halcyon, Shearwater and XDEEP for making this issue possible. We also want to thank Nicole Alarid, Orie Braun, Jared Hires, Nick Hollis, Michael Thomas, and Patrick Widmann, who helped us sort out sidemount configurations and Elena Vivaldo for researching recreational sidemount. And of course, we want to thank our models: Robert Thomas (CDG), Ricardo Castillo (Dive Rite), Emöke Wagner (Halcyon), Melodie Trevino (Hollis), Marcelin Nebenhaus (Razor), Mélissa Bezaz (Toddy) and Tamara Adame (XDEEP). Looking good divers! We do plan to create a free downloadable poster from this issue. Watch this space!
Please note, we realize this issue primarily represents the views of advocates who are making a case for sidemount. We haven’t focused on stories of divers who have had bad experiences with sidemount or spent much ink delving into its downsides, to the extent that these exist. Consequently, I invite readers who feel so moved to submit their views and or experience, call it, “The Trouble With Sidemount … ” or “Never Do This is Sidemount..” . I’m joking about the titles but serious otherwise. We will happily run thoughtful stories. Let’s get a conversation going.
Finally, we would like to acknowledge that as human diving journalists and artists on deadline, we have likely made errors and omissions, and/or failed to identify important items that our geeky readers will no doubt discover. Our apologies in advance. If you do find any errors, omissions, or needed tweaks, please let us know, and we will endeavor make corrections. Thank you.—Michael Menduno/M2
Please take a minute and complete our new: Sidemount Diving Survey. We will report the results in a coming issue.
Use the following navigation links to dive into your favorite configurations
Halcyon ZERO GRAVITY™ Sidemount System
Cave Diving Group (CDG) Sidemount System
The CDG sidemount system has evolved many times since the 1960s but it’s still a lightweight system for diving sump’s generally found after significant dry caving. The important thing to remember is that it is not just one system. Each diver will have a slightly differently made harness but basically doing the same thing.
Weight System
- Traditionally the weights go around the waist on a CDG harness, a more modern version of the CDG harness such as the RMTD harness (in the photo) weights can be fitted down the spine.
Harness
- The harness itself is a simple design with minimal adjustment but designed to walk or cave while wearing wetsuits and small cylinders. It can also be used with larger cylinders. Steel cylinders are the norm for uk cave diving. The harness has fixed D rings and no sliding D rings for use with Aluminium cylinders.
- Some CDG harnesses are adapted to use with vertical access equipment (SRT) so the caver/diver can descend the vertical dry cave then use the same harness to dive.
BCD/Wing
- The CDG harness has no wing, because generally buoyancy is not required when using wetsuits and small cylinders in sumps. It was common for divers in British Sumps when using drysuits to use the suit for buoyancy and use no wing. In more recent years a small wrap around wing such as the X deep classic or home made equivalent can be easily added if the diver is using bigger cylinders or carrying equipment through the sump to further dry cave exploration and requires buoyancy.
Commentary
The CDG harness is designed to take weight loading on the divers’ shoulders and hips. Karabiners are generally used for attaching cylinders to the harness. A bolt snap is not a weight loading piece of equipment and should not be used to lower equipment down and then up vertical sections of dry cave, karabiners also work when covered in mud or grit! It’s not a harness that will get cylinders in that perfect internet trim but it is a harness designed to explore flooded cave sections found a long way underground. All modern harnesses took the sidemount system from the original Cave Diving Group harness design.
Dive Rite Nomad Ray
The Nomad Ray is the latest sidemount system offering from Dive Rite. It includes a number of notable upgrades to the Nomad range and was designed to be easily adjustable, suitable for a range of body types and diving applications, including the use of both steel and aluminum cylinders.
Weight System
- The Nomad Ray has three padded, internal pockets each of which can hold up to 5 lbs/2.3 kg of either hard or soft weight.
- The weight pockets are located on the back of the wing and accessed via a zipper, making for easy weight adjustments while fitted.
Harness
- The harness consists of independent shoulder, waist/hip, and crotch straps each of which are adjustable to fit the system to a variety of diver body types.
- The harness incorporates custom hardware including two fixed angled D-rings on the shoulders, two fixed angled D-rings on the waist/hip strap plus, two sliding waist D-rings, two chest bungee-retainer slides, two rear drop D-rings for primary tank attachment, and one “dog-bone” crotch strap double D-ring for accessories, plus a DPV D-ring.
- The harness is in Y configuration and attaches to the BCD/wing via woven D-rings at the top and through woven loops and screwed connection at the bottom.
- For the fashion conscious, the wing comes in six colors.
BCD/Wing
- The BCD wing is shaped to provide lift at the lower lumbar region. It comprises a Denier outer shell with an inner bladder and has 42 lbs/19 kg of lift.
- The upper backside panel is abrasion-resistant for restrictions.
- It incorporates a standard inflator that can be routed from the left (standard) or right side.
- The BCD includes two pull dumps which are also OPVs. One is located at the inside top center of the wing with a left shoulder pull dump activated via a sheathed cord. The second is located at the bottom left of the wing. The locations of the dumps may require an alteration of diver position to dump all of the gas from the wing e.g. roll to the right to dump from the left side lower dump. Note this would also align with dumping gas from a drysuit.
- “Belly-band” bungees locate and wrap the outer wing extremities to the diver’s body. The bungee includes a bungee hook attachment and two wing grommets for easy and quick adjustments by simply moving an overhand knot on the bungee.
Commentary
The Nomad Ray is a significant upgrade for Dive Rite and evolving to meet the needs of modern sidemount divers. In particular, the easy-access weight system, shoulder dump, easy-to-adjust “belly-bungee,” plus the method of attaching the harness and the independent crotch strap to the wing, are notable improvements.
Halcyon ZERO GRAVITY™ Sidemount System
Halcyon’s Zero Gravity sidemount system was a collaborative creation with our Mexico distributor, Zero Gravity. The Zero Gravity system puts the buoyancy over the hips and along the sides of the rib cage where buoyancy is desired. Extremely streamlined, the air chamber positioning gives it a flat profile on the back of the diver. The Zero Gravity is suited for double aluminum 80’s and a wetsuit or small steel cylinders used with dry suits and heavier undergarments. The Zero Gravity features an adjustable harness, and an optional weight pouch that will hold up to 15 lbs./6.8 kg, and optional inflator placements on the right or left side.
Weight System
- The added weight attachment is designed and built to lay on the diver’s back in line with the spine. Like our traditional weight options, this allows the diver to keep perfect trim while adding weight. With the three-pocket design, you can add up to 5 lbs/2.3 kg in each pocket as needed and disperse them at different placements for that balanced distribution. The velcro additions allow for secure storage and keep even soft lead pouches from moving around while diving.
Harness
- A harness system with multiple point adjustment is styled after the standard backplate harness, with the lower portion of the strap going behind the diver, allowing for greater freedom of movement and comfort, especially for the women in the diving. This harness system is easily changeable when needed over time, allowing the diver to modify the colors of the webbing if desired for personal customization.
- The newly redesigned door handles provide divers with several options when choosing the right cylinders and placement. With the added grommets, the diver can adjust the door handles into three different locations on the back, as is, higher, or in towards the diver’s back. This placement is essential when setting up the cylinders. The added feature of using curved door handles over traditional square door handles is that when the cylinders are clipped to the system, the bolt snaps do not snag or get hung up in a corner. This keeps the cylinders and the bolt snaps in a free space for easy reaching, clipping, and removing as needed throughout the dive.
- The adjustable bungees make it easy to use with different regulator configurations, whether the regulator is pointed up or down. The waist strap D-rings on the right and left hip allow for AL80’s to be clipped forward as they become buoyant. We achieve this with a non-fixed D-ring by adding an O-ring to the design. This allows the D-ring to be in an upright position for easy finding and clipping while at the same time allowing the D-ring to move freely if in a tight passage or corridor without becoming a snag point.
- The uniquely positioned cylinder bungee runs across the back of the system and diver giving you more stretch when wrapping your valves while keeping your cylinders high, tight, and secure. This placement of the bungee allows the diver to adjust the bungee length very easily, whether in training or for the more experienced sidemount divers. This bungee is very easy to change out by the user if they prefer a lighter or heavier bungee without compromising the design of the system.
BCD/Wing
- The streamlined design with a unique U-shaped bladder provides an almost free and clean back that reduces your profile and drag. The U-shaped bladder allows stable, uniform lifting along each side of the diver where they need it and across the rear of the diver so they have adequate lifting potential without sacrificing profile and trim. This keeps the profile of the diver very low enabling them to access smaller passages without rubbing the bladder. Top to bottom while trim position does not change even as the bladder is fully inflated. This was a key component in the design for low-profile passages and doorways.
Commentary
“As an avid sidemount diver and explorer in North Florida, I have used a variety of side mount systems on the market. It wasn’t until I dived the Zero Gravity system, that I was able to pass through several low passage tunnels without feeling the top of the system scraping along the way. The low profile of the system, even when fully inflated, allowed me as the diver, to keep a low profile in the cave system. This truly became a game changer when it came to exploring new tunnels.” – Orie Braun, Halcyon Sales Manager
Hollis Katana 2
The Katana 2 is the latest sidemount offering from Hollis and brings them into line with the other top contenders in the sidemount space.
Designed with support from cave explorer Edd Sorenson, the Katana 2 incorporates a number of innovative features including a “Quick-Fit” system for easy adjustment, the ability to configure as a H or Y style harness, out of the box support for the KISS Sidewinder, and a BCD top dump valve with shoulder pull.
Weight System
- The Katana 2 weight system features a drop-in Velcro pouch design with 4 x 5 lbs/2.3 kg pockets along the spine. The spine positioning of the weight system can assist with trim adjustment as required.
Harness
- The Katana 2 sidemount harness features an innovative “QFS” Quick Fit System which allows users to easily tailor the one-size-fits-all harness to their specific size.
- The design also allows for either an “H” or “Y” style harness configuration. H-style is most commonly used when donning the system in a drysuit and can be less restrictive, while the Y-style is most similar to a backplate configuration and provides a snug but comfortable fit when properly sized. Both are suitable for various types of diving and user preferences.
- The Katana 2 is the first harness with attachment loops built-in to support the popular KISS Sidewinder CCR and similar units now in the marketplace.
BCD/Wing
- The wing lift capacity is 40 lbs/18 kg and features a tapered design to keep the diver profile as low as possible, without the “turtle shell effect” which causes drag.
- The top of the wing is two-
Commentary
“The coolest thing about the Katana 2 is the way it ships out of the box. You can customize it to your preference thanks to the innovative harness and adaptable wing design. Technical divers love to customize their gear … and they can make all of the adjustments themselves without permanent modifications on this rig.” – Hollis Brand Manager, Nick Hollis
Razor
The Razor Harness embodies simplicity and elegance with just two continuous pieces of webbing and one closure point. Its design is minimalistic, yet strong, rugged, and reliable. The harness offers a comfortable and custom fit for divers of all sizes, thanks to its quick and easy setup and adjustable, standardized hardware.
Weight System
- The Razor Harness allows precise placement of weights for optimizing trim. Additional weights can be easily added to the Razor Pocket Weight, the Waist Strap, or both if more than 13 lbs/6 kg are needed.
Harness
- All attachment points, such as D Rings, on the Razor Harness can be swiftly and easily adjusted for personalized equipment placement. Each Shoulder Strap/Waist Strap can be adjusted at the Mini Back Plate.
- The length of the Lumbar/Crotch Strap can be adjusted at the Delta Shoulder Plate. The height of the Waist/Hip strap can be adjusted at the Mini Back Plate. Extra attachment points can be added if necessary.
BCD/Wing
- The BCD/wing is simple to use and attach or detach from the Razor Harness, secured by just two button head bolts. The mounting position can be easily adjusted to accommodate different-sized divers.
- The wing is exceptionally durable, constructed with three layers: two outer layers of abrasion-resistant 1000 denier ballistic nylon with a layer of heavy gauge polyurethane in between. The wing is ultrasonically welded, and all edges are finished with edging tape. All attachment points feature reinforced grommets for added strength.
- The primary wing provides 45 lbs/20 kg of lift and is equipped with a low-profile, heavy-duty manual dump/OPV valve from DSS, along with a standard power inflator. This allows inflation of the primary wing either using the power inflator or orally.
- The fittings for the dump valve and corrugated hose/power inflator are interchangeable, enabling divers to use them on either the left or right side of the wing according to their preference.
- The Redundant wing also provides 45 lbs/20 kg of lift and is fitted with a very low-profile “coin” dump/OPV valve and oral inflator.
Commentary
The Razor Harness and BCD/Wing system offers divers a sleek and minimalist design without compromising on functionality or durability. Its simple yet robust construction provides a comfortable and secure fit for divers of all sizes. The weight system allows for precise weight distribution to optimize trim, while the adjustable attachment points offer personalized equipment placement. The BCD/wing is easy to attach and remove, and its rugged three-layer construction ensures long-lasting performance. With interchangeable fittings and low-profile valves, the system offers versatility and convenience. Overall, the Razor system combines simplicity, reliability, and versatility, making it an excellent choice for divers seeking a streamlined and efficient diving experience.
Toddy Style
The Toddy Style Sidemount System offers divers a unique and innovative approach to sidemount diving. Its “sandwich” style weight system, adjustable harness, and thoughtful design elements enhance comfort, balance, and ease of use. With the ability to customize weight distribution, easily adjust harness straps, and utilize specialized clips, this system provides divers with a streamlined and efficient sidemount experience. The Toddy Style Sidemount System is a reliable choice for divers seeking enhanced maneuverability and minimal drag during their underwater explorations.
Weight System
- The “sandwich” style system consists of a thin backplate that holds the wing together while protecting it from accidental restriction impact. A backmount-style backplate finishes the sandwich-style system. These backplates also act as a weight system. If the user desires, additional backplates can be added, fitting perfectly on top of each other and distributing the weight evenly over the diver’s back, rather than concentrating it on the spine. This allows for better balance and reduces the “rotation” effect.
- For divers who want to travel with the system, there is a more traditional sidemount weight system. It consists of a weight holder that can be added to the backplate, again placed away from the spine, to enhance balance and minimize the “rotation” effect.
- Finally, there is a flexible butt extension with a special mount for precise addition of weight to achieve optimal trim.
Harness
- The system’s shoulder straps are easily adjustable using a Velcro system that secures it in place with wide elastic wraps.
- The shoulder straps are connected by a removable bungee that keeps them in place when divers turn on their side. It also acts as a temporary clipping place for items such as pigtail marker clips, lights, etc.
BCD/Wing
- The inflator extends from behind, near the neck area, resembling the position in a backmount system. There is no valve, but instead, a direct, extremely durable, and resistant connector. This eliminates a fragile point present in all other systems.
- The wing’s bladder is easily accessible and can be changed even in the field.
Regulator accessories
- The system also utilizes custom-made clips for the regulator’s second stages. These clips allow divers to secure the regulators to their chest D-rings, resulting in a more streamlined profile and easy access in case of an emergency.
Commentary
The Toddy Style Sidemount System stands out as a top choice among cold water backmount divers looking to transition smoothly to sidemount diving. It offers a convenient alternative because of its compatibility with both existing regulators and hose lengths, as well as not requiring dedicated cylinders. The presence of a backplate, reminiscent of traditional backmount setups, provides a sense of familiarity and ease of adaptation. Whether for cold water diving or any other diving environment, the Toddy Style Sidemount System offers divers a reliable and comfortable sidemount configuration to enhance their underwater experiences.
xDEEP STEALTH 2.0 Tec
The STEALTH 2.0 TEC was designed for deep decompression diving and extended cave penetrations. It provides 42 kbs/19 kg of lift to support multiple cylinders required for advanced diving. It effectively manages gas movement and position to ensure stability, balance, and trim at any inflation level.
Weight System
- The Xdeep Stealth 2.0 features a customizable central weight system located on the spine. It can be adjusted to accommodate the maximum weight preferred by the diver.
- Additionally, there are droppable weight pockets available in different sizes: S-size (2 x 4.4 lbs/2 kg), M-size (2 x 6.6lbs/3 kg), and L-size (2 x 13.2 lbs/6 kg).
- For fine-tuning trim purposes, there are also trim pockets in M-size (2 x 4.4 lbs/2 kg) or L-size (2 x 6.6lbs/3 kg) that can be placed anywhere on the harness.
Harness
- The harness is one universal size with a wide adjustment range. It consists of independent shoulder, waist/hip, and crotch straps, each made of different thicknesses and fully adjustable with tri-gliders to fit various diver body types.
- The harness utilizes custom hardware, including two fixed large D-rings on the shoulders, two fixed D-rings on the waist/hip strap, and two rubber sliding waist D-rings (metal version available as an upgrade).
- It also has two rear drop square attachments for primary tank attachment, a crotch strap D-ring for accessories below the dump valve, and a DPV D-ring.
- The Y-configured harness attaches to the BCD/wing at the top.
BCD/Wing
- The BCD wing is designed to provide lift at the lower lumbar region. It is constructed with a Cordura 1100 dTEX outer shell fabric and a Nylon 440 dTEX inner bladder with a 0.2 mm TPU coating. It offers 42 lbs/19 kg of lift.
- The upper backside panel is abrasion-resistant for durability.
- The BCD includes an inflator available in three sizes, with a standard length of 16″/41 cm (14″/36 cm and 19″/48 cm available upon request).The inflator can be routed from the left (standard) or right side.
- One central low pull dump also functions as the system’s OPV.
- Bungees keep the wing attached to the waist harness, ensuring a snug fit around the diver’s body.
- The wing’s color combinations can be customized on Xdeep’s website: https://tuneup.xdeep.eu
Commentary
The XDEEP Stealth 2.0 is a well-designed and versatile diving system that caters to the needs of deep decompression diving and extended cave penetrations. Its robust weight system, adjustable harness, and efficient gas management make it a reliable choice for advanced divers. The BCD/wing combination offers ample lift and durability, while the customizable options allow divers to personalize their gear. Note that the modular system can also be configured from recreational sidemount. Overall, the XDEEP Stealth 2.0 combines functionality, comfort, and performance, making it a strong contender for serious diving adventurers.
Please Take a Minute And Complete our New: Sidemount Diving Survey. We will report the results in a coming issue.
Steve Davis is the producer and host of the acclaimed podcast, “Speaking Sidemount,” author of the books, “The Canterbury Wreck – A Diver’s Guide” and the eBook, “Sidemount Fundamentals.” He is a specialist sidemount diver/instructor, dives exclusively in sidemount, and is the principal instructor and founder of Sidemount Pros. Steve travels the world diving sidemount in caves, wrecks, and open water. Through Speaking Sidemount Steve’s mission is to share his passion for sidemount diving and provide a medium for the world’s top sidemount divers, instructors, and explorers to share their experiences and thoughts on sidemount diving.
Stratis Kas, a Greek-Italian professional diving instructor, photographer, film director, and author, has spent over a decade as an esteemed Advanced Cave instructor, leading expeditions to extreme locations worldwide. His impressive diving achievements have solidified his expertise in the field. In 2020, Kas published the influential book “Close Calls,” followed by his highly acclaimed second book, “CAVE DIVING: Everything You Always Wanted to Know,” released in 2023. Accessible on stratiskas.com, this comprehensive guide has become a go-to resource for cave diving enthusiasts. Kas’s directorial ventures include the documentary “Amphitrite” (2017), shortlisted for the “Short to the Point” Film Festival, and “Infinite Liquid” (2019), which explores Greece’s uncharted cave diving destinations and was selected for presentation at Tekdive USA. Kas’s expertise has led to invitations as a speaker at prestigious conferences, including Eurotek UK, Tekdive Europe and USA, Tec Expo, and Euditek. For more information about his work and publications, visit stratiskas.com.
Michael Menduno/M2 is InDepth’s editor-in-chief and an award-winning journalist and technologist who has written about diving and diving technology for more than 30 years. He coined the term “technical diving.” His magazine “aquaCORPS: The Journal for Technical Diving” (1990-1996) helped usher tech diving into mainstream sports diving, and he produced the first tek.Conferences and Rebreather Forums 1.0 & 2.0. In addition to InDepth, Menduno serves as an editor/reporter for DAN Europe’s Alert Diver magazine, a contributing editor for X-Ray mag, and writes for DeeperBlue.com. He is on the board of the Historical Diving Society (USA), and a member of the Rebreather Training Council. Menduno is the organizer of Rebreather Forum 4.
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