Sidemount diving in open ocean – is there ever a good reason for it?

By Yvonne Press

Sidemount diving’s roots lie firmly in sump diving and cave exploration. It started as a means to an end. Sidemount allowed cavers to further explore dry caves and navigate flooded passages. It made it possible for divers to explore restrictions they otherwise wouldn’t be able to before. And it has now taken on a life of its own turning into one of the most popular courses across training agencies. 

Some may describe it as a fad, certification numbers seem to suggest that sidemount diving is here to stay. In South East Asia, TDI and SDI report a steady growth of certification numbers of around 10% each year between 2017 and 2018. There was a 30% peak increase in 2017 following the release of new training materials in 2016. Other agencies report similar trends. 

While many divers take up sidemount to get into cave diving, just as many dive sidemount dive in open water. There are plenty of reasons for choosing this configuration.

Balance and Stability 

First off, sidemount provides better balance and stability than diving with a single or even double backmounted cylinders. Quite simply, with sidemount, you have one cylinder on each of the diver’s sides and aligned with their torso. This provides a more stable and streamlined position in the water compared to a single-cylinder on the back. It effectively turns you into a platform. The buoyancy characteristics of the cylinders themselves also promote diving in trim or working position, something all divers should aspire to. 

Flexibility and Configurability 

Next, there are flexibility and configurability. Do you want to use one cylinder or two? The answer may depend on boat logistics and the purpose of the dive. However, personally, I prefer the redundancy and balance of two over one and I don’t believe kitting up is that different between the two options. Though, if simplicity and a speedy entry are key to the success of the dive, the argument might turn the other way. 

Sidemount diving does not necessarily require specialized cylinders. This makes (well-trained) sidemount divers fairly low maintenance guests on dive boats. Distinct left and right-handed valves are preferable, but not always available. They are something that’s generally only found in specialist tech dive shops. Many divers will manage with simple DIN valves. 

Can you sidemount dive with standard, unadjustable valves and yoke adapters? Theoretically, yes, and if divers find themselves in a remote location with no other option it will allow them to get in the water. However, much of the intention and reason for the existence of sidemount diving has to do with streamlining and creating efficiency. Using yoke adapters goes against those by creating entanglement hazards and making first stage connections bulky.

Comfort and Safety 

Another set of reasons include comfort and safety. 

  • Starting with safety, with valves being positioned in front of the diver, gas shutdowns are straight forward even with limited mobility. 
  • First stage leaks are easily detected and dealt with. 
  • Equipment handling before and after dives can be easier with sidemount as divers can carry one cylinder at a time to and from the entry point. Technical divers are often expected to handle their own equipment and twinsets are not always easy to move around for every diver.
  • Others prefer sidemount as it relieves the strain on their back. 
  • Photographers enjoy the increased ‘headroom’ allowing them to look in each direction without being limited by the position of a manifold. 

Lastly, it comes down to personal preference: divers are allowed a choice of the equipment in which they want to dive, just as they are expected to be competent in the handling of this configuration.

Safe Exploration 

Possibly one of the biggest reasons for sidemount diving – is enabling safe technical diving exploration and opening up new areas for technical divers. In remote areas, technical divers may not find twinsets nor CCR supplies available. However, in order to truly explore a new dive spot, decompression dives are almost always required. Sidemount allows divers to do this safely while diving a streamlined, efficient configuration allowing for redundancy in gas supply and other life support equipment. This makes sidemount quite simply the perfect tool for opening up new tech diving territory with limited equipment supplies. 

Logistically Easier 

  • Technical or sport – from small boats such as RIBs or small fiberglass boats, especially those not customized for technical diving it’s easier to stow single cylinders compared to twinsets. 
  • Diving sidemount allows divers to make more efficient use of the space available, making for an easier life for crew and passengers alike. 
  • Loading and cylinder handling are also often easier with single cylinders. Most divers are able to lift a single sidemount cylinder up to the boat crew, but fewer can do the same with a set of twins. 
  • The opportunity to don and doff equipment in the water: with or without the help of crew kitting up and de-kitting in the water are usually possible unless conditions require a negative entry. This avoids awkward moving around on the boat before getting on the water. Of course, it is possible to don and doff twinsets in the water, but it is certainly more difficult than clipping and bungeeing individual cylinders.

Another reason to take your sidemount kit into the open ocean is to retain, improve or practice overhead environment diving skills. Not every cave diver lives in cave country but keeping skills fresh is vital for safe dives on that next cave or wreck diving trip.

Not without limitations 

Having talked about reasons for sidemount diving, it’s worth looking at its limitations or potential downsides. 

  • There is the somewhat more involved gas management, requiring divers to regularly switch between regulators to keep cylinders at similar pressures. 
  • Then there is the question of how many sidemount cylinders are practical. Personally, I draw the line at four for comfortable diving – two back gas cylinders and two deco gases. Having practiced with six, I believe the flexibility gained with up to four cylinders is completely taken away by six cylinders forming what feels like a suit of armour around the diver’s front. 
  • Some believe that diving from large boats can be difficult in sidemount configuration. From a sidemount instructor’s and a diver’s perspective, much depends on the diver’s competence with the configuration and their ability to adapt to different diving circumstances. 

This is where much depends on training: sidemount is misunderstood as simply putting two cylinders on your side and setting off into the water when it is much more than that. Every attachment, every piece of hardware and every inch of bungee added or cut make a difference – to donning, doffing, cylinder handling and comfort in the water. Understanding the intricacies of the different moving parts and a will to ‘play’ and adjust their configuration long after the end of the initial certification course are landmarks of great sidemount divers. With that in mind, sidemount can be perfect in just about any situation.

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