Advanced 9 minutes
Sidemount: tanks on the sides, and why it changes so much
Real redundancy, access to tight passages, and a learning curve you have to respect
The first time someone sees a diver in sidemount, they usually think it's an aesthetic quirk. The second time (when they see that diver pass through a crack their double tank wouldn't fit through, or enter the water without carrying twenty kilos on their back) they get what it's about.
In this article you'll see where the sidemount configuration comes from, how it's rigged, what problems it solves (redundancy, access, logistics, and trim), how gas is managed by alternating tanks, and how it really differs from conventional back-mounted rigging.
Sidemount is the most common gateway to gas redundancy, and also a configuration that's often adopted as a trend and executed poorly. This article is educational material and doesn't replace the specific course, where the gear is fitted to each body.
Where it comes from and what it solves
The configuration was born in cave exploration, where tight passages and sumps made a bulky back-mounted rig impractical. Carrying the tanks at your sides lets you get through restrictions, take off a cylinder and push it ahead of you, and put it back on: something simply impossible with a double on your back.
From there it jumped to general technical diving and, later, to recreational diving, where it solves different problems from the original ones. The first is redundancy: two independent tanks, each with its own first and second stage, mean a gas failure affects half your supply, not all of it.
The second is logistical, and it shouldn't be underestimated: you enter the water without carrying the weight on your back. On a shore entry, on a boat ladder with surge, or for someone with back problems, the difference is huge, because the tanks are clipped on once you're in the water.
The third is hydrodynamics and trim. Properly adjusted, the profile is flatter and more compact than a back-mounted double, and balance is fine-tuned by moving the attachment points.
And the fourth, more prosaic: two eleven- or twelve-liter tanks are far easier to handle, transport, and carry than a double joined by a manifold.
Keep reading with full access
This article is part of the full Encyclopedia. A donation from USD 10 unlocks every article, every species photo and the downloadable app, and helps sustain the Scuba Sign Paperless Diving Community project.