sidemount diving ocean

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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5 replies
  1. Geoff Infield
    Geoff Infield says:

    I just returned from a liveaboard in PNG where I was the only Sidemounter. We had open water guys doing 45m on singles with little idea of the impact of depth on consumption (warm bright sea makes everything look easy and fun!) and all I could think of was that if one grabbed another’s octy, they’d quickly run out and it’d cascade.

    I USED to I think sidemount’s biggest benefit in open water was making twice the gas and redundancy accessible to even NEW divers – I started my sidemount course on just dive 16 and instead of worrying about cylinder shutdown drills and isolation and hearing bubbles I couldn’t see behind my neck, everything was in easy reach and visible.

    But NOW that I’m using my TDI ER cert to enjoy cheap 55m dives everywhere, I’ve realised that sidemount’s biggesty benefit to me is that I can pack a couple of stage straps, go anywhere in the world, strap ANY TWO TANKS on, and have twice the air and redundancy.

    It’s so easy that I once strapped a 15 litre steel on one side and an AL80 on the other, using STRING to mount the 15 cos my hose clip didn’t fit lol. Brilliant.

    And with gauges point straight up (forward when prone, angled slightly inwards) I don’t even turn my head to check gas pressures. They can snag a little in ships but its easily changed.

    It’s the only system that guarantees ANY shop or boat will be able to offer you two tanks, anywhere. Just brilliant!

  2. Andrew
    Andrew says:

    And interesting article – I had the opportunity to dive with some tech side mount divers recently and I have some observations.
    Firstly side mount underwater does look great underwater – very streamlined with good trim. And I like the idea of having visible access to the regs and valves – it makes shutdowns very easy to deal with.
    However for open water boat diving what I saw gave me some serious concerns about the safety both for the side mount divers and anyone else on the boat.
    The first observation is that side mounts take up a lot of space when kitting up. That 12-diver boat is not going to hold that number of side mount divers! If diving in tidal waters everyone needs to be getting ready at the same time or run the risk of missing slack water and side mounts make divers VERY wide. You cannot get two side mounted divers kitting up in the same space as two back mounted divers. We were a group of 7 (4 side mounts and 3 single tank divers) and we filled the boat – could have taken one more diver possibly.
    The next observation is that the nature of the set up is that there is a lot of movement in the cylinders. A good back mount is bolted in place and will not move. A side mount is clipped on and is not rigidly attached to the wing or back plate. This makes moving around a boat in any kind of sea state other than flat calm extremely hazardous. Once the momentum of a moving cylinder catches the diver the chance of a slip or a fall is greatly increased. This puts the diver and the other guests at a pretty substantial risk. This was especially the case when kitting up. It didn’t look like there was room to kit up whilst sitting down. So picture a rocking boat, standing up with one cylinder clipped on and struggling to reach round to clip on the second bottom clip.

    In our case we were giant striding off the back of the boat – so I can’t say what it is like to roll off the side. Or what it is like from a boat with very high freeboard (think Scapa Flow charters)

    The gear you dive with should be applicable to dive itself including the dive location – in this case a boat. I think side mounted gear is very applicable in cave diving but that doesn’t mean it translates to open water boat diving. (I feel the same about harnesses with no break at the shoulder after witnessing a diver who had fallen on his back struggle to get out of his gear on a rolling deck).

    The benefits of a good back mounted twin set far out-way any advantage of a side mount on the open seas. So unless your goal is some serious wreck penetration – keep the side mounts for the caving.

  3. Scott S.
    Scott S. says:

    Thank you for writing this fantastic article, Yvonne!
    It resonated with me and I completely agree with your closing statement “sidemount is misunderstood…” and, unfortunately, the area I dive in is an example of that.

    In my cold water part of the world, one of the most important components to enjoying and excelling in sidemount is missing – proper training. This lack of adequate training has been creating an environment of negative opinions, frustrated divers, and boat operators that cringe when sidemount cylinders are brought aboard. All because the majority of sidemount divers here are being trained to hang their cylinders instead of mount them, route their hoses in strange loopy configurations, figure out on their own how to exit and enter dive boats, and sound like sonar buoys while their diving “ping, ping”.

    With that said, there are a few of us out here that did our research and found instructors that primarily dived sidemount and who not only understood the difference of diving in 45º/7C waters but knew how to configure a few sidemount systems to work beautifully in it.

    Today, thanks to proper sidemount training and regular skill practice, I enjoy diving sidemount in cold open water and inside wrecks just as much as my warm water friends do exploring cave systems.

  4. Ted Reitsma
    Ted Reitsma says:

    I agree fully with your article and the comments by others so far. I have been side mounting for a few years. The basic course give you the basics. As you said length of even a bungie cord can make a difference. I took Steve Martins online 100hr douse ( which covers more than side mounting. I learned a great deal more that I did not know before and was not in any printed courses and it was invaluable for my dives- provided greater enjoyment and safety. Helped take some ‘kinks out of the armour’ would be the most accurate description. I think having 2 independent systems should be mandatory. With all the benefits you already mentioned, the only drawbacks are cost, and as a one of your respondents said, can make a RIB (rubber boat) more crowded. Saying that, it was great handing the tanks to the RIB operator and climbing on with my BCD still on where everyone else had to doff their gear- much heavier for RIB operator to lug onto the boat.


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