Scuba Diving with Sidemounts: What is it?

Scuba Diving with Sidemounts: What is it?

Is sidemount just a fad, or should we all move our cylinders off to the side?

What is a sidemounted scuba unit? If you’re a regular diver who dives in popular locations from time to time, you have very likely seen a novel site recently: SCUBA divers without any dive tanks on their back, but rather one slung under each arm. In other words, you’ve seen sidemount divers.

Sidemount is the new trend making waves in the diving community. From a strict niche element only a few years ago, it has gone mainstream.  Most manufacturers now feature at least one BCD rigged for sidemount diving.

PADI recently introduced a sidemount specialty, and with the newest update to their policies and standards, so does NAUI. But what’s with the craze?

Scuba diving with sidemount

Sidemount and training gives perfect trim - Jon Milnes

A different way of cave diving

Sidemount, like the use of double cylinders, comes from the world of tech diving. Whereas the traditional method of wearing the cylinders goes all the way back to the original Aqualung, Invented by Jacques Cousteau et al. The idea of wearing them under your armpits stems from the world of British cave diving.

British caves, unlike those of the American’s, in particular in Florida (the mecca of US cave diving), aren’t big, open tunnels, but rather narrow, and often very low-ceilinged environments. There taking up as little room as possible is often necessary if you’re the have a chance of penetrating a cave.

Hence, the idea of moving the cylinders from the back and to the sides, one under each arm, slung in a custom harness and attached to the BCD. A special type of BCD is required, but apart from that, everything else is standard equipment.

The pros

The main advantage to sidemount is that the diver takes up less space in the water total, and in particular along the vertical axis when horizontal. This allows the diver too much easier maneuver in tight spaces, such as small caves or wrecks.

Also, valve drills - shutting down a free flowing cylinder and switching to the other one - is much easier. As both valves and regulators are within view of the diver, and not stuck onto his or her back. This makes these emergency procedures, which can be a matter of life and death, much simpler to do, especially in a cumbersome dry suit and thick undergarments.

Also, any valve leakages, while unlikely, can be detected quickly by the diver.

Technical diver with sidemount tanks

Technical scuba diver in the shallows - Paul Cowell

The cons

The primary problem of sidemount is that it doesn’t scale quite as easily as traditional backmount. A backmounted BCD can quite easily be converted from taking double cylinders to taking a single cylinder. Whereas a sidemount BCD is much easier when you to use double cylinders, even on a shallow reef dive.

This makes it quite likely that you’ll need two BCD’s, one for single cylinder diving and one for doubles/sidemount.

Scaling the other way can also be problematic. For deep, prologed dives, divers carry more than just two cylinders, as the same gas cannot de breathed throughout the dive.

Tech diver dives with twin tanks

Jon Milnes

A number of gasses are used during the descent and ascent, called “travelling gasses”, and another gas is used during the bottom part of the dive.

When using a backmount setup, these extras cylinders are carried as stage bottles slung over the shoulders and carried under the arms of the diver. Of course, with a sidemount, you already have cylinders there to begin with, you on really demanding dives you quickly run out of real estate by your sides. Regardless of how many cylinders you can carry under your arms, you can also have two more cylinders total when diving backmount.

Finally, prolonged walks before reaching the water, as is often found around places like the Mexican cenotes, can be harder with sidemount, as a placement on the back allows for a better weight distribution.

To get a feel of this, try carrying an amount of weight distributed in two shoulder bags, one at each side, then try moving the same weight into a backpack.

To side or not to side?

The choice of sidemount or not is a personal one, as many things are in diving. If you diving environment features many narrow passages, as the British caves mentioned earlier, sidemount can definitely be an advantage.

If you need to travel far and deep, backmount might be a better choice, as well as if you need to walk a lot of surface between gearing  up and hitting the water. Outside of these scenarios, go with whatever works better for you. But do remember to take a sidemount course before launching into it.

Have you ever dived with Sidemounts? Or would you like to try it? Tell us in a comment below!

About The Author

Thomas Grønfeldt Senger

Thomas is a Naui Instructor and has been diving in Australia, France, Egypt, Sweden, Indonesia, Iceland, and numerous other locations around the world.


  1. Chris

    Thanks for trying to simplify the side mount trend right now. As a diver who has a variety of technical dive training I still have a hard time “getting it.” I understand and appreciate side mount diving in caves with low restrictions, but for the general diver it seem like so much extra effort. We have had a few side mount divers on our dive boats and most of them don’t make it look easy or convenient. But it was a good article, thanks.

  2. Richard Youell

    ” Whereas a sidemount BCD always requires you to use double cylinders, even on a shallow reef dive.

    This makes it quite likely that you’ll need two BCD’s, one for single cylinder diving and one for doubles/sidemount”

    This depends on the make of BCD
    I used sidemounts last week and asked that very question and was shown the back of the BCD with a strap on it to allow it to accommodate singles as well as sidemounts.

    • Torben Lonne

      Did it add a single tank on the back? I would think it very uncomfortable if there is no plate on the back. Or am I mistaken? thanks for sharing!

  3. Richard Youell

    Our SMS100 Sidemount system was designed not just with the sidemount cave divers in mind, but any diver. Whether you are a beginner, advanced or technical diver, this kit was designed for you. Suitable for sidemounting twin or single cylinders, but also for use with rebreathers or rear mounted singles. This “go anywhere” system can be used in any environment from open water to the overhead environment. Ready to dive out of the box.

  4. Richard Youell

    This is the actual BCD that I had. Very comfortable, Easy to unclip both cylinders and re-clip for getting into tight spaces- seemed to be “lighter” than a conventional rear mounted cylinder???? and the balance was unbelievable!
    I then watched as the instructor then mounted a further two cylinders to his BCD. From what I witnessed I believe this BCD can accommodate no less than SEVEN cylinders but why you would need 7 on an open water course is beyond me, lol

    • Torben Lonne

      Nice to know. Thanks for sharing! Are you still using it?

  5. Richard Youell

    No, this was the one that the dive school gave me to try out

  6. Jay Skiba

    Yes, you can do sidemount with one tank. I have seen them do it and believe it is just setting up your trim with minimal counterweight.

    • Torben Lonne

      Hi Jay,

      Yes it’s possible, but does it make the dive experience better?

  7. De Bruyne Alain

    I dont know who have being writhing this article buth for shure he or she dot have a clue what sidemount diving is, let stand alone that they practise sidemount diving. Yes you can dive single or double cylinder sidemount whit every availeble SM set on the market, and no there is no problem in attaching 3 – 4 or even 6 cylinders on a sidemount harnes. you just need to consult the writh SM instructor, wich organisation dont mather just pick a good instructor

    • Torben Lonne

      Hi De Bruyne,

      Thomas, who wrote the article, does not state that it’s not possible to dive with 1 or 6 tanks, but that it will be easier t bring more tanks with back plate bcd, as two on the back and two the side, is easier than 4 on the side. All is possible, but what is best? On a one tank dive, would you prefer sidemount or backmount? And why?

  8. Mark

    Badly researched and just lazy – could even get pictures – pics one and three are of rebreather divers.
    Con – the hybrid range of Sidemount BCDs from Hollis and diverite (sms100 / sms75 and nomad range offer single and double backmount support through cam band slots for single and 11inch grommet holes for banded doubles.

    • Torben Lonne

      Sorry the pictures are not correct, they’ve been corrected now!

  9. Tim

    Good article. As somebody who dives and teaches sidemount diving, one thing that I believe should be in there is that sidemount is less forgiving than backmount when it comes to foundational skills – proper weighting, buoyancy control, trim.

    On backmount, and even on backmount doubles, an overweighted and out-of trim diver can still kind of get by, at least in open water. Just look at the illustrations in the PADI TecRec manual and you know what I mean.

    On sidemount, bad trim means that instead of being nice and super sleek as you should be, you present a profile like a slightly floppy barn door – less streamlined and much less stable than you would in backmounted doubles with the same kind of trim. It looks and feels uncomfortable, and you’ll quickly get task loaded and stressed out when called on to do something like a valve shutdown drill, shoot a surface marker buoy, or pass one of your cylinders to your buddy. With the proper training however, diving sidemount can be rather liberating, with better streamlining, easier balance, vastly greater mobility, and less strain on the spine.

    Therefore, kids:
    – Don’t let anybody sell you a two-day sidemount course! You’re short-changing yourself!
    – Choose your instructor carefully. Recreational agencies are cranking out sidemount instructors by the boatload. A newly certified sidemount instructor may have as little as 20 dives on sidemount – and that’s including the dives in his own training! Ideally you want to dive with them and how they look underwater. At the very least, ask a few questions about their experience, including experience in technical diving and overhead environments on sidemount.

  10. Mark


    Sorry I find four Sidemount cylinders just as easy to dive as two backmount and two side stage/deco tins and that the cylinders are all streamlined in SM as opposed to the two stages hanging almost vertical – like the doubles diver in the article ( I SM my stages too)

  11. De Bruyne Alain

    Torben, i am a technical sidemount diver so i dive regulary with stages/deco cylinders, i still find diving sidemount with 4 cylinders safer and more axesible then backmount. what the diving with 1 cylinder concerns, with an alu 80 cu or an low pressure (200 bar) steel cylinder there is no problem i dont even have to put a counter weight. Now once i shouldt need 6 cylinders to perform a dive i wouldt consider going backmount and sm my stage and deco cylinders. buth i am not at that point yet.

  12. Spyros

    The truth is always somewhere in between.

    Sidemount is a tool and there are plenty of variables on how you can setup the cylinders and the rest of the gear.

    This i means is that there are cases that BM is ”easier” instead SM. Maybe they are just a few but they exist.

    The point is to avoid speak or write black or white.

  13. Jim

    Silly article. Full of half truths and some outright false information. The comments indicate the level of incompetent instruction out there as well. I teach recreational sidemount and use it in open water. I also teach tech classes in it. The trek through the jungle remark clearly shows a lack of understanding on how to transport the tanks to remote sites. Only an idiot would wear them for long walks unless using something like lp 50 cylinders or al 40’s.

  14. eric

    just curios why does the picture show your spg tucked under the rubber hose retainer?

  15. Remy B.

    I dive sidemount with a single or double, Rec or Tec without issues or been uncomfortable, I started like everybody else with single backmount, went to Doubles backmount and now Sidemount. Sidemount outpass safety, Solo, travel, deep, flexibility and streamline to single or double backmount.

    The comments from the Author are completely off, clearly not a sidemount diver, it is like having a OW diver writing on a Rebreather article.


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