Why I Dive Sidemount, Redundancy, Balance and a Few Hard Truths

Ask ten divers why they dive sidemount and you will get ten answers, and at least three of them will start with the word caves. I understand the association. Sidemount grew up in tight overhead spaces where a diver simply could not fit through with cylinders on their back. That story is true, but it is only the beginning, and it has left a lot of open water divers thinking the configuration has nothing to offer them.

So let me put the case properly. Sidemount is not a cave trick that escaped into the wild. It is a way of carrying gas that solves real problems for reef divers, wreck divers, technical divers and anyone whose back has started sending them polite complaints after a day of lifting cylinders. In this post I want to give you the reasons that actually hold up, and I want to be equally clear about the parts nobody should sell you.If I had to reduce the whole argument to one word, it would be redundancy. In sidemount you carry two cylinders, one on each side, and each is a fully independent gas supply. Each has its own first stage, its own regulator and its own valve. There is no manifold joining them, which means there is no single point of failure that can drain both at once.

Think about what that buys you. If a first stage fails, or an O ring blows, or a regulator starts free flowing, you have lost the use of one cylinder. You still have a second, complete, working gas supply on the other side. In the worst realistic failure you lose half your gas, not all of it. That is a very different situation to face than a total loss, and it changes how calm you can afford to be while you deal with it.

There is a second, quieter benefit. Both cylinders sit in front of you, in your field of view, within easy reach of your hands. You can see a leak. You can trace a hose. You can shut a valve down and open it again without contorting to reach behind your head. Problems that are visible and reachable are problems you can solve. That is the heart of why so many self reliant divers trust the configuration.The next reason is harder to put into words until you have felt it, so I will borrow a description you hear a lot in the community. Good sidemount is the closest thing to freediving that you can do while carrying gas. The cylinders tuck along your body, the kit stops feeling like something bolted onto you and starts feeling like part of you.

That is not just a nice sensation. A streamlined diver has less drag, and less drag has real consequences. You move through the water with less effort, which means you breathe less, which means your gas lasts longer and your legs are fresher at the end of the dive. Lower gas consumption is not a marketing line, it is a direct result of not dragging a large frontal profile through the water column.

Balance matters too. With a cylinder on each side you can fine tune your trim, and you can keep adjusting it through the dive as the cylinders empty and your buoyancy shifts. When it is set up well, you sit flat and still in the water without fighting for it. I will come back to that word, because there is a debate hiding inside it.Here is the part that convinces divers who could not care less about cave lines. Sidemount is kinder to your body and your logistics.

Instead of heaving one heavy back mounted set, you carry two (smaller?!?!) cylinders, one at a time. You can move them to the water separately. You can gear up in the water rather than standing on a rocking boat or a slippery shore with a full rig on your back. For anyone with a history of back or knee trouble, and for all of us as we get a little older, that difference is not cosmetic. It is what keeps people diving for more years.

The flexibility runs further than lifting. You can don and doff the rig in the water. You can split it, hand a cylinder up to the boat, then hand the rest up. It works from a small boat and it works from a shore entry. That adaptability is why a lot of divers who tried sidemount for one reason ended up keeping it for a completely different one.Let me say this plainly, because the myth is stubborn. Sidemount works for wreck diving, including penetration where space is tight. It works for open water reef diving where you simply want the redundancy and the streamlining. It works for deep and technical diving where independent gas supplies are a serious safety argument. Caves are where it was born, not the boundary of where it belongs.

I know divers who came to sidemount purely for warm water reef trips, because gearing up off a small boat suited their life better than a heavy twinset. The configuration did not ask them to justify themselves against a cave. It just worked.There is a phrase I keep coming back to, and it captures the whole thing. Backmount is a system you wear, sidemount is a system you interact with. Once you have it on your back, a back mounted set is largely fixed, you carry it and you trust it. Sidemount asks more of you and gives more back.

In practice that means you are working with the rig throughout the dive. You feel the cylinders, you notice when one is running lighter than the other, you make small adjustments as gas moves and buoyancy shifts. Some divers find that constant involvement tiring at first, and that is fair, it is more to think about. But most who stick with it come to love exactly that relationship, because a rig you interact with is a rig you understand, and a rig you understand is one you can trust when something goes wrong.

This is also why I tell people not to judge the configuration on their first few dives. The interaction has to become second nature before it feels like freedom rather than homework. Give it time in the water and the fiddliness fades into instinct.If I only gave you the good news, I would be doing you a disservice, so here is the other half.

Sidemount will not fix bad buoyancy. It will expose it. If your buoyancy and trim are shaky, strapping cylinders to your sides does not hide the problem, it puts it on display for everyone in the water to see. A diver who is not in control looks worse in sidemount, not better.

Following from that, bad sidemount is worse than good backmount. A sloppy rig, dangling hoses, cylinders at the wrong angle, a diver crabbing along at forty five degrees, that is not just unattractive, it is less safe and less efficient than a tidy back mounted set. I will be blunt, poorly done sidemount is simply horrible to watch and worse to dive.

It also demands correct setup and regular practice. The skills fade fast if you rarely dive the configuration. Valve drills, regulator handling, cylinder trim, the muscle memory of clipping and unclipping, all of it needs maintenance. And buying the harness does not make you a sidemount diver, any more than buying a guitar makes you a musician. The kit is the beginning of the work, not the end of it.There is one point worth pulling apart, because you will hear both versions and they sound contradictory.

Some divers say the side cylinders help you sit flat, that the weight low on your sides settles your trim and does some of the work for you. There is a grain of truth in it. Placement of mass does affect how you lie in the water.

Experienced instructors push back on that framing. Their point is that sidemount does not give you good trim, it reveals whether your trim is already there. If your fundamentals are solid, the configuration lets them shine. If they are not, no arrangement of cylinders will save you. I lean towards that second view, but I want you to hear both, because the honest answer is that mass placement helps a little and skill helps enormously, and it is a mistake to expect the kit to do the diver’s job.If you value redundancy, if you want to move through the water with less effort, if your back would thank you for lifting two (small?!?!) cylinders instead of one heavy set, and if you are willing to put in the practice, then yes, whatever kind of diving you do. There is a neat way I like to frame the difference. Backmount is a system you wear. Sidemount is a system you interact with. If you enjoy that interaction and commit to it, it will reward you well beyond any cave.If this has you curious, my advice is to try it properly with an instructor before you spend a penny on kit, because a good first session in the water tells you more than any article can. I would love to know what pulled you towards sidemount, the redundancy, the streamlining or a grumpy lower back, so leave me a comment and tell me.