Have you ever noticed other divers around you with two or more cylinders? There are obviously various ways (configurations) to carry your cylinder(s) underwater.
In this article, I will go deeper into the sidemount configuration – what it is, the perks and drawbacks, and for whom it is useful.
Scuba Cylinder Configurations
In the picture above, you can see me using a sidemount configuration, in Northern Indonesia. It’s one of the four common configurations:
- The classic single tank backmount setup;
- Two tanks on the back, commonly known as a twinset;
- Two tanks, one on each side of your body, known as sidemount;
Attention: Changing your configuration requires proper training by a qualified instructor.
Most (if not all) of us learn to dive with a single cylinder on the back. This is the easiest configuration to learn and the most convenient way to dive. It is fast to assemble and to gear up.
Instead of focusing on the equipment, you can mainly enjoy the underwater life, focus on the diving itself and build up experience. This remains perfect for the majority of people who dive occasionally and have no interest in going into technical diving.
A twinset is a set of two interconnected tanks, also carried on the back, but it takes a bit more knowledge and practice to set it up and to use it during the dive. The reason to dive this way, obviously, is to have more air.
Rebreathers are described in this article here.
First of all, there is often a discussion between sidemount divers and twinset divers about which system is best. I will not participate in that discussion and won’t compare them, as I believe the best approach is: “Use the right tool for the right job.”
Sidemount diving found its roots in the cave diving community. Flooded caves offer great diving opportunities, but they pose a lot of additional challenges compared to the open water.
One of those challenges is narrow passages. A bulky cylinder on your back may simply prevent you from going further in that direction, so there was a need for another system that offers more flexibility. That’s where sidemount diving came into the picture.
The cylinder is no longer on the back, but alongside the body, with the valve protected by the armpit. If your body can pass, so can the cylinders.
Equipment: Backmount vs Sidemount
Most of you are probably familiar with the basic requirements of backmount diving, so we’ll use that setup to compare with sidemount diving.
Wing & Harness
As the cylinders go alongside the body, the first change is that the classic BCD (buoyancy control device) is replaced with a harness and wing.
The harness is the webbing that fits snuggly on your body. The wing is attached to the harness and only inflates on your back. This offers a great deal of stability and comfort in the water, without any pockets or bladders on the side.
The cylinders are clipped onto the harness using D-rings, bolt snaps, and bungee rope. There are also hybrid systems that can accommodate both sidemount and classic backmount cylinders.
As there are usually two cylinders, there are two independent regulators. One with a short hose, which goes around your neck, and the alternate one on a long hose (typically 7 ft or about 210 cm). The long hose is the one you would use if you must provide air to a diver who ran out of air.
The weights are typically integrated into the harness. You can still use a classic weight belt but, it is an oddity in sidemount diving.
The cylinders are the same as in back-mounted diving. This means you can easily bring your sidemount equipment with you on holiday without the need for special tanks. Because they go on your sides, you need extra clips and accessories to keep them in place.
Advantages of Sidemount Scuba Diving
So what are the advantages of a sidemount system for recreational divers?
Personally, I like the redundancy of air when diving with two cylinders. That is the number one reason for me. When one regulator or cylinder fails, there is always a second one ready to use.
Two cylinders also means you have more air to share in case one of your buddies on a single tank has a problem.
Secondly, I find it much easier to get in the correct diving position (trim) compared to using a regular BCDs. I feel more free as well, because there is nothing on my back.
This is closely related to streamlining where you fix your gear in such a way that it creates the least amount of water resistance. That is harder with a tank on your back.
Third, problem solving is easier. Because the first stages are under your arm, they are visible and reachable. So if there is a major problem, you can shut down one tank and breathe from the other. This means you are more independent than someone diving backmount.
The final advantage I want to mention is especially important for people with back problems. Carrying the tank on the back may be a painful or even dangerous challenge. So whether you dive from a boat or from the shore, you can always attach the cylinders while in the water and never need to carry them the conventional way.
Drawbacks of Sidemount Scuba Diving
As with almost anything in life, sidemount diving also has some drawbacks.
First of all, the preparation takes more time. The cylinders need to be properly set up, which is a more time-consuming task than the classic setup.
Secondly, clipping the tanks to your harness in the water, or just before entering the water, is an extra step. So generally you might be slower than other divers.
The same is valid for getting out of the water. It may be even more challenging in a current or when the surface is very choppy. Support from the boat crew is usually required.
Finally, you need to pay extra attention to your air consumption because you manage two independent tanks. You need to switch from one regulator to the other several times during the dive so you keep them at similar pressures.
Divers Who Go Sidemount
So, which types of divers may consider sidemount diving?
We already know that cave divers use this type of configuration, but it’s a great match for recreational divers, too, as it offers extra safety and independence.
There are also underwater photographers and videographers. They may just need that little extra time (and thus air) to take that award-winning shot they had in mind. That octopus or frogfish may not be there when you want them to be there, so you need to be patient. That is inherent to nature photography in general.
Wreck divers will also benefit from a sidemount system, the same way cave divers do. When you go inside the wreck, you may have to go through smaller passages. A sidemount configuration also allows you to detach the cylinders and push them ahead of you, so you can squeeze through even smaller restrictions.
Finally, there are the technical deep divers who go beyond the 130 feet (40m) depth limit, which is considered the maximum depth for recreational diving. The deeper you dive, the higher the surrounding pressure and thus the more gas you consume. When you ascent from a deep dive, you must make multiple stops along the way to avoid decompression sickness. You need to have plenty of air (or other gases) to complete these kinds of dives in a safe manner.
Precaution for Overhead Environments
Cave, wreck, and decompression dives have one thing in common. They are overhead environments, as opposed to open water. In a cave and wreck, there is a physical ceiling. In deep diving, there is a physiological ceiling related to the risk of decompression.
This means that in any of these types of dives, it’s impossible to make a direct ascent to the surface in case of serious peril.
Having that extra air is a requirement for training in any overhead environment. Related to the nature of caves and wrecks, there is an added risk of being stuck or getting lost, so the riskier the dive, the more precautions you should take. Obviously, sidemount helps you mitigate those risks.
So, Yeah or Neah?
Despite the skepticism about using a sidemount setup by recreational divers, I am a strong believer.
And just like with any other specialty, it keeps you in the water while you expand your knowledge and skills. Two birds with one stone.