Historically, sidemount diving was for extreme, technical divers who used the configuration to penetrate small sections of caves. But its adaptability and advantages have been discovered by divers of varied experience levels, and that, coupled with advances in equipment and greater availability of training, has made sidemount diving an increasingly common application. It’s not just for cave divers anymore. Sidemount diving is a gear configuration in which a diver wears a tank on each side of his body instead of mounted on his back. Sidemount diving tanks lie parallel to the body, below the shoulders and along the hips. Since the tanks are not connected by an isolation manifold, as they are in a backmount configuration, the diver has two separate and redundant sources of gas and will breathe first from one tank and then the other, switching back and forth between two independent regulators throughout the dive. The clips on the bottom of the tanks are attached below the hip, and the top of the tank is secured with a bungee system, which allows the tanks to ride along the side.

The advantages of sidemount diving first resonated with advanced and technical divers who realized that wearing tanks on the side of the body created a lower profile in the water than traditional back-mounted tanks, thereby allowing access to, and the exploration of, small spaces without disturbing the environment. Less silt equaled greater access. Wreck divers discovered they could push a tank ahead of them into a small hatchway by simply unclipping the bottom portion of the tank from the butt-plate. Cave divers saw the same benefits when working their way through low, overhead passageways. Reef divers, too, implemented sidemount diving to improve the navigation of tight coral canyons while hopefully reducing unintentional coral contact.

But whether diving a wreck, cave or reef, every specialty recognized the safety benefits of sidemount diving. A sidemount configuration gives a diver easier access to tank valves in an emergency. Some divers carry sidemount “bailout bottles” specifically for this purpose. Sidemount rigs make it easier when divers need to swap out extra tanks staged along a tagline or the floor of a basin. The position of the tanks also gives the diver’s head greater range of motion for enhanced vision and comfort.

One final advantage for sidemount enthusiasts is simply the management of what can be a heavy load. Considering the average technical rig weighs approximately 130 lbs., it’s easy to see the appeal of a system that allows for the placement of tanks in the water ahead of the diver, allowing him to enter the water in nothing more than a basic harness system. The tanks then clip in, but with the weight burden significantly reduced through buoyancy. Of course, when the dive is done the process is easily reversed, allowing divers to exit the water with the same ease. Older divers and petite women are two dive demographics increasingly embracing sidemount diving for these very reasons.

Sidemount configurations are proving a good fit with the increasing popularity of rebreather diving. Because of the cluttered front presented by rebreather hardware, the side-mounted “bailout bottles” provide an unobtrusive way to carry an emergency air supply. The sidemount tanks also provide a ballast of sorts, creating a more streamlined profile and manageable center of gravity.

Like all forms of specialized diving, divers should seek training to learn about sidemount diving. Experienced technical divers already accustomed to gas management and dealing with multiple cylinders and the rule of thirds will likely figure out how to sidemount with the help of a good workshop emphasizing the ergonomics of the system. Even then, it will likely take quite a few dives to balance the rig just right and to make the operation intuitive. Every diver must decide if these adjustments are a puzzle to solve on his own or a special skill set to hone with the help of an instructor.
Divers who are not technically trained yet want to get started in advanced diving with sidemount should take a structured course. Proper training will include removing a bottle underwater and swimming while pushing the tank in front of the body, donning tanks while floating at the surface, air sharing, gas management and deploying a surface marker. Working with an instructor will help the diver configure the finer nuances of the rig, set up the tanks properly and make sure the trim is correct in-water. Courses are typically run over two days.

Divers should choose an instructor who is familiar with their intended dive environment. There are differences between sidemounting from a boat or a cave or a wreck, and the best instruction is scenario-specific. Divers come in a variety of shapes and sizes with a variety of needs; ensure your instructor is knowledgeable on the various sidemount options and can teach you what you need to know.

To find the rig that works best, a potential sidemount diver needs to do a thorough assessment of his dive environment and understand how personal body type and buoyancy characteristics affect a rig. Don’t try to squeeze custom needs into a “one-size-fits-most” configuration. What are your rig lift needs? Do you need your rig to be easily adaptable, or do you need one highly specialized for a specific environment? A cold-water diver may wear heavy steel tanks and need a rig designed for that environment, including a wing with enough lift for the tanks, materials that are cold-water friendly and adjustment points that can be handled with thick gloves. Cave divers in Florida may need something entirely different, and deep wreck divers off New Jersey may require something else again.

Pay attention to safety features: Do they meet the needs of your dive environment? If you plan to sidemount from a boat, you should make sure your rig is designed with the proper safety clips in case you have to enter or exit the water with the tanks attached to your harness. (This can happen when a boat encounters rough seas and transporting the tanks one at a time, unattached to the diver, can be difficult or dangerous. Rather than stress or snap the bungee system, the diver uses the clip located on the neck of the tank to clip into something more robust, like a harness D-ring.)

Divers planning to squeeze into restricted spaces with protrusions need to pay attention to the placement of the inflation hose and bungee system, along with other potential snag points. A buttplate tucked beneath a wing would be a potential problem, and the inflation hose should have a protective sleeve and a low profile. A continuous, one-piece bungee system is not necessarily considered the safest alternative; the prevailing trend these days is two separate bungees. That way if one bungee is sheared, you won’t lose control of both tanks. Keep in mind that safety and redundancy in advanced diving is critical.

Both recreational and technical certification agencies now offer sidemount training, making it easier to find an instructor. More and more sidemount divers are seen on boats and at dive sites; as part of your due diligence, ask their opinion on why they choose to sidemount and what safety features are critical to the dive environment. There’s a wealth of information eagerly disseminated among those early adapters of the equipment. For while it’s not necessarily mainstream just yet, sidemounting has definitely come out of the cave and into the light of day.

© Alert Diver — Summer 2010