Sidemount: Not Just for Caves Anymore

Ten years ago, if you showed up to an open water wreck dive in sidemount, people would ask if you’d made a wrong turn on the way to the cave. Today it’s a regular sight on deep recreational dives, stage-and-deco rigs, and increasingly just as a recreational configuration preference. The gear culture around it has shifted.

But sidemount has also picked up a certain mythology — some divers swear it fixed their back, transformed their trim, made them a better diver. Others tried it and went back to backmount within three dives. The truth is more nuanced than either camp usually admits.

Let’s talk about what sidemount actually is, where it genuinely shines, where backmount still wins, and what’s involved in actually using it well.

What Sidemount Is

In a backmount configuration, your primary cylinder (or doubles) rides on your back. In sidemount, your cylinders ride horizontally at your sides — clipped at the hip and at the first stage, with the cylinder valve angling across the front of your body within easy reach. You can access both valves, reach both first stages, and even remove and reattach cylinders underwater.

The rig is modular. You can dive it with a single cylinder (rare but possible), two cylinders for redundancy and extended gas, or add stages and deco bottles the same way any other tech configuration does.

Most sidemount setups use a harness with a wing-style BCD integrated or attached, though there are older-school DIY approaches. Quality dedicated sidemount BCDs from manufacturers like Hollis, Apeks, Scubapro, and others are now widely available.

Where It Actually Came From

Cave diving. Specifically, the low, silty, narrow caves of Florida where backmount doubles physically don’t fit. The early pioneers were working through restrictions measured in inches, needing to pass their equipment ahead of them and reconnect it on the other side. Sidemount solved a mechanical problem.

The configuration then migrated into wreck penetration diving, where similar restrictions apply — though usually without the silt factor. And from there, the broader tech community picked it up.

The Real Benefits

Overhead environment access. This is still the core use case. Sidemount lets you work through horizontal restrictions that would stop a backmount diver cold. If you dive caves or wrecks with tight passages, it’s not a preference, it’s a requirement.

Redundant gas with accessible valves. In backmount doubles, your valves are on your back. If you have a valve problem, you need either a long manifold or a dive buddy. In sidemount, both valves are at your sides and reachable without contortion. For valve drills and gas management in tech diving, this is a meaningful advantage.

Surface handling and transportation. This is underrated. Two separate cylinders are much easier to carry, transport, and handle at the boat or shore than a set of steel doubles on a plate. You can enter the water in stages — particularly useful for shore dives with awkward entries.

Easier cylinder filling management. Two 12-liter cylinders filled to different fractions (say, different nitrox mixes for a deco dive) are easier to manage separately than a twinset manifolded together.

Back comfort for divers with injuries or issues. This one requires nuance — more on it below.

The Back Pain Conversation

Let’s address it directly, because it comes up every time sidemount is discussed: “My back was killing me in backmount and I switched to sidemount and it fixed everything.”

Sometimes true. Sometimes not.

Sidemount distributes weight differently — cylinders at your sides instead of on your back. For divers with specific types of back issues, particularly those aggravated by lumbar loading in a vertical position (at the surface), this can be genuinely beneficial. You’re not strapping 20+ kilograms to your back and waddling to the water.

However, sidemount has its own postural demands. You need to manage cylinders banging against your hips, and the horizontal weight distribution requires its own trim discipline. Divers with shoulder or hip issues sometimes find sidemount creates different problems than it solves.

If you’re exploring sidemount for back pain reasons, try before you buy. Rent the gear and do a few pool sessions. Don’t drop $800 on a harness based on someone else’s experience.

The Honest Trade-Offs

It is harder to trim. Backmount, especially with proper doubles weighting, is relatively forgiving — the gas symmetry keeps you stable. Sidemount cylinders need to be individually balanced and their position constantly managed. New sidemount divers almost always look lumpy in the water for a while. Getting genuinely flat and stable in sidemount takes more practice than backmount.

Gear setup takes longer. Rigging a sidemount system correctly — correct D-ring positions, proper bungee tension on the cylinder necks, correct clip placement — is fiddly. Experienced sidemount divers do it quickly, but there’s more to it than clipping into a backplate.

Stage cylinder management doubles up. If you’re adding actual stage bottles to a sidemount rig for very long dives or deep deco profiles, you now have four cylinders to manage. That’s a lot of hardware. Some tech divers who need that gas volume find backmount doubles with stages simpler to manage in the water.

Cost. A dedicated sidemount BCD is comparable to or slightly more expensive than a quality backmount BCD. Budget $400–900 for a quality harness. You’ll also need properly rigged cylinders — single cylinder configurations need to be set up differently than backmount singles.

Who Should Seriously Consider It

Wreck and cave divers. Full stop. This is where sidemount earns every penny.
Tech divers doing deep dives with deco obligations who prefer valve accessibility.
Shore divers doing long swims who want to manage heavy gear in stages.
Instructors and divemasters who dive constantly and want flexibility across environments.
Divers with documented back issues who have actually tested sidemount and found relief.

Who It’s Probably Not For

Recreational open water divers diving to 20 meters in warm water. Backmount is simpler, lighter, and perfectly fine.
Divers who want a “magic fix” for poor trim. Trim comes from buoyancy practice, not gear configuration.
Anyone who hasn’t taken a proper sidemount specialty course. The configuration requires specific skills — running your gas correctly, managing valve positioning, proper cylinder attachment — that you need to be taught, not YouTube’d.

Getting Started

If you’re interested, take a sidemount specialty with an instructor who actually dives it regularly (cave divers make excellent sidemount instructors — they live it). Spend time in a pool before your first open water sidemount dive. Expect it to feel weird for a few sessions.

It will click. And when it does, the access and flexibility it gives you in overhead environments specifically is worth every frustrating pool session.

Whether you’re diving doubles, sidemount, or a deco rig, Abyssi’s dive log handles multi-cylinder gas tracking so you can record what you actually breathed and plan smarter next time. Start logging your tech dives.