Scuba Diving with Sidemounts: What is it?
Is sidemount diving 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?
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. It is then vital to reduce the amount of space you take up as possible when penetrating a cave in UK waters.
Hence, the idea of moving the cylinders from the back 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 requires standard equipment and business as usual.
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 scuba 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 drysuit with thick undergarments on.
Also, any valve leakages, while unlikely, can be detected quickly by the diver.
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, prolonged dives, divers carry more than just two cylinders, as the same gas cannot de breathed throughout the dive.
A number of gasses are used during the descent and ascent, called “traveling gasses”, and another gas is used during the bottom part of the dive.
When using a backmount set up, 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 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 your 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 into a cave on foot, backmount might be a better choice. If you need to walk a fair distance between gearing up and hitting the water, a sidemount is cumbersome and tiring. Outside of these scenarios, go with whatever works better for you. But do remember to take a sidemount course before launching into it without experience.