Sidemount Diving

Published by rdevanney on

Divers like the one facing the camera may utilise sidemount tutorials to gain tips and tricks on various aspects of sidemount.

Sidemount diving

Without wanting to insult your intelligence, sidemount diving involves positioning cylinders so that they sit parallel to your body, on either side of the torso. Simply put, it’s just another way to carry your diving equipment around with you. But it’s more than that, much more. You can use one cylinder or two, and undertake technical decompression dives as you would with a twinset.


A sidemount BC consists of two parts- a harness, and a wing. Commonly they are joined together as one system. The harness “spine” sits on your back, and is attached to shoulder and waist webbing,  plus a crotch strap. Think of someone abseiling; it’s the same principle. Metal d-rings on the waist allow you to clip the lower half of a tank to the harness, and bungee coming from the spine can be wrapped around the valve of the tank to keep it in place. When everything is configured properly, the tanks should be horizontal to the body on either side when the diver is horizontal. It’s not nearly as complicated as I just made it sound.


Origins of sidemount diving

The “seed” for sidemount was sown by cavers in the UK. As they ventured further into dry cave systems, they encountered sumps; essentially areas that collect large volumes of water.


The only way to see what lay beyond was to dive into these sumps to see if they led back to dry caves. Initially, and I’m talking 1934 now, they devised an airtight hood with a long hose, so they could “extreme snorkel” their way through. If you think I’m joking, watch the documentary- A cave diving story. Although many of the sumps were less than a metre (3ft) deep, the ease of breathing was insufficient, to put it mildly. To prevent suffocation, hand pumps were used. This made life a little more bearable. However, no mask, BC, or fins were used.


The 1960s

Fast-forward to the 1960s and scuba was being used to help push further into these sumps. Crude harnesses were worn, so that small scuba cylinders could be placed in an accessible location- usually on the leg. This was so they could be removed and re-attached easily as they passed through tight spots or “restrictions” as they are known.


The 1970s

Tally ho, forward to the 1970s, and word got through across the pond about this “English system”.  Unlike the caves in the UK, where occasional sumps interrupted large networks of dry caves, in Florida, caves are fully submerged. Therefore, exploration is done solely with scuba equipment.


It didn’t take long for Floridian divers to start messing around with this style of diving. It wasn’t a case of just strapping the tanks on and away they went. Cylinders had to be streamlined and positioned so that buoyancy and trim were easy to maintain. This is where cylinder placement at the sides began properly, with the valves tucked underneath the armpits.


The 1990s

Not sure what happened in the 80s; more homemade harness development dressed in denim, walkman, roller blades and mullets.


Up until the 90s, any sidemount diving was done using modified scuba gear that was readily available. The first dedicated sidemount set-up available to buy was developed by Lamar Hires at Dive Rite; the “Transpac”. This type of harness was bulky because it needed large amounts of lift to cope with the weight required for cold water drysuit diving and steel cylinders. This setup became known as the “American system”.


In 2001, the Armadillo harness was released, which incorporated cylinder attachment with bungee, and had the BC further down the body.  A butt plate was also added to allow additional cylinders to be attached. Other manufacturers brought out their own versions of American systems, Hollis being a notable one. But even until as recently as 2010, there wasn’t much choice of dedicated sidemount BCs. They were all cumbersome to wear.


The “Mexican system”

A few years later, various manufacturers started selling a distinctly different style of sidemount system. The idea was minimalism- a bare skeletal harness, and a streamlined wing more suited to using aluminium cylinders. This became known as the “Mexican system”. Hollis, OMS, and UTD had their own, and Steve Bogarts developed the Razor system, which was quickly seen as the benchmark for this style. It didn’t take long for other companies to follow suit; Xdeep, Hollis, UTD, Aquamundo, Apeks, and IST to name the most popular brands.


This leads us up to the present day. All the aforementioned brands are now bringing out second or third generations of their BCs. Recreational versions, tech versions, cave pouches, double bladders, it’s all happening. Because they’re now so simple to set up, adjust, and wear, sidemount is increasing in popularity every year. This is especially true among recreational divers, and it can only be a good thing to make technical diving more accessible.


Why learn sidemount diving- what are the advantages?

There are many reasons to want to dive sidemount. Maybe you want more gas, or to be less dependent on your buddy. Or perhaps you just want to try something new. It’s also a more accessible route into technical diving.


You have twice the gas compared with standard single-tank diving. No, you don’t have 400 bar (6,000 PSI)- a common misconception! If using Aluminium you have 2 cylinders at 200 bar (3,000 PSI). You have greater volume at the same pressure; 4,400L of gas instead of 2,200L with two standard 11L (S80) cylinders.


You also have redundancy of supply. If you have a free-flowing regulator, you can turn off the valve and switch to the other tank, or even “feather” the valve- turn it on and off as you breathe. If you have a problem with your gas, it’s much easier to deal with. The valves are positioned underneath the armpits, so you can pull them forward to see what’s going on, and then easily turn a valve off if you need to. No more desperate reaching behind you to feel (or not) what’s happening.


Having twice the gas means longer dives. If you use nitrox, you can take advantage of longer NDLs more effectively. On a single tank, you often get low on air before your NDLs get low. So a shallow sidemount dive on nitrox will give you longer dives in the 20-30m range (100-130ft). Did I mention that the diving position is very comfortable too?


Another advantage of sidemount diving is if you have back problems or are classed as a small human. You can get in the water wearing the harness and BC and put the tanks on at the surface. At the end of the dive, you can remove the tanks and get out of the water. This varies, depending on whether your entry/exit point is a shore (beach, pier, jetty), or diving from a boat. It also depends on the diving conditions; removing gear in big waves or strong currents is not easy and potentially unsafe. But overall, not having to lug heavy tanks back onto the boat is a huge advantage.


There are many cylinder choices for cold water divers- 2x 12L, 2x 7L, or 2x 8.5L steel cylinders. These can be 232 bar or 300 bar and it depends on how much weight you want to carry and your preference for gas volumes. Of course, there’s nothing to stop you from going with 2x 11L Aluminium cylinders either. It’s just that steel cylinders help offset the need to carry extra weight with drysuits.


Are there any disadvantages to sidemount diving?

If you’re diving somewhere that requires a long walk to the entry or exit point, it can be a pain to carry two cylinders all the way there and back. But that’s just the way it goes with diving. The alternative is one trip with a twinset or single tank on your back. A minor disadvantage is that many dive resorts still don’t have modular valves on their cylinders. But that’s not the end of the world, you can still dive sidemount.


If you’ll be doing a lot of dives in the 100m+ range (330ft), sidemount does become more difficult to manage in terms of extra decompression cylinders. It can be done up to 60m, but in my opinion, backmount is just easier. Rebreather more so.


Perhaps the most salient disadvantage to you, is that you will have to buy two high-performance regulators and a sidemount harness. Not the cheapest things in the world, but once you have them you have them for a long time. Consider it an investment. If you buy regulators with swivels and a 5th port adapter, you can use the same regulators for sidemount and back mount, with a little switching around where the hoses exit the first stages.


So now you’ve decided that sidemount is a brilliant option for diving, don’t beat yourself up that you left it this long to learn.



What does a sidemount course involve?

Let’s get one thing out of the way. Training should be a steep learning curve. There’s a lot to take in. You must learn the ins and outs of how the harness works and how it needs to fit. This is the most important part of learning sidemount. If the harness is wrong, everything else will be wrong. Then you learn how to properly attach the cylinders to your harness, and understand how to set the regulators up correctly. It shouldn’t just be a case of “this is how the longhose goes”. It should also include “this is why the longhose is like this”, and “this is another way to do it, but I do it this way because ……..”.


This is all before you get in the water. None of it is difficult, it’s just a lot of information to comprehend and absorb. It takes time to practise all these things. If you choose to do a 2-day sidemount course, things will be left out, no question. Courses should be 3 or more long days and include 4-6 long dives.

In water, the first thing you will notice (provided that the set-up was done correctly), is just how comfortable and easy it is to dive on sidemount. Buoyancy is intuitive, and staying horizontal is not difficult, provided you don’t have bad habits like dropping your knees and not arching the back (this is incredibly common- think of the position when riding a motorbike).


Awareness in sidemount diving is much less challenging than on a twinset because there is nothing behind your head and the diving position is naturally more comfortable. A lot of the skills and diving procedures will be new. But having a solid base in terms of buoyancy and trim makes things much less challenging than when diving on a twinset for the first time.


For divers who have already learned to dive in a twinset, the learning curve is not quite as steep. You’re already aware of redundancy and propulsion, and the importance of awareness, good buoyancy, communication and positioning. The main things to wrap your head around are the equipment set-up and the differences in how the skills are undertaken.


How do you find a good place to learn?

There are a few things to consider. First, does the instructor know what they’re doing? That seems like a ridiculous statement, but let me elaborate. When sidemount started to become popular, many instructors saw it as a way to gain more customers. Incredibly, many diving agencies allow instructors to self-certify. This means they pay money to PADI for example, and away they go, they’re now a sidemount instructor- with no real knowledge or experience of sidemount. You can see how that might be a problem.


Talk to potential instructors

When looking for a sidemount instructor, look at photos or videos of them on sidemount, it will help to give you a sense of what they are about. Ask them if they dive with different sidemount harnesses. Ask what their experience of sidemount diving is beyond teaching it, and what kind of diving they use sidemount for. Ask what environments they use sidemount in- wreck, cave, cold water, warm water etc.


Also ask how long the course is, and how many dives? 2 dives and 2 days are just not enough. Will you learn how to set up more than one type of harness? Do they dive in cold water? There’s no point in learning sidemount in a wetsuit with an instructor who has never dived in a drysuit if you intend to dive sidemount with a drysuit.


Online sidemount courses

Nope. You can only learn sidemount in person, with your hands on the equipment, setting it up with someone there to guide you. Whilst there is value in watching videos to give an already qualified sidemount diver tips and tricks, you need to spend time in the water with an instructor helping you.


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