Sidemount your tanks? Why would you? Here’s 7 reasons


By Steve Davis, Tech Sidemount Instructor and host of “Speaking Sidemount” podcast

When you ask a sidemount diver what they love most about sidemount they invariably include the word, “freedom”. They say the feeling of sidemount diving is akin to freediving, the feeling of being one with the water and able to move through it freely in any orientation. This feeling of freedom and weightlessness is divers’ nirvana and one of the very real reasons sidemount diving has experienced such growth.

There are of course, other reasons such as sidemount being fit for purpose when diving in caves, mines, sumps, and wrecks where the ability to navigate through narrow restrictions is a requirement. But there are several other fundamental benefits that sidemount diving brings and which make it a good choice for any diver looking to move to multi-cylinder, open circuit diving.

So here’s my top seven reasons why you should dive sidemount.

For working in tight spaces… (HMS Canterbury) (Photo: Brian Hadfield)


Whenever watching a dolphin, seal or shark moving through the water it’s so easy to marvel at how effortless their movement is. They have evolved over many millions of years developing the speed and maneuverability they need to become the successful marine predators they are! Since water is 800 times denser than air its hydrodynamic drag means that an increase in speed requires a many-fold increase in propulsive power. Therefore, reducing drag by streamlining is a vital component of moving efficiently through the water. Yet for some reason some people pay scant attention to streamlining. Many divers are trimmed down at the feet which means they present a large surface area to their direction of travel.

This causes unnecessary drag and extra effort required to move through the water. It results in higher gas consumption rates too, but more worryingly, can increase diving stress especially when working at depth or in currents. So how does the sidemount configuration address this? Sidemounting your cylinders correctly means all your cylinders align with your body and your direction of travel. This makes propulsion easier and diving becomes much more relaxed and comfortable.

It is still a mystery to me why so many experienced technical divers wear their deco/stage cylinders at near right angles to their body, almost as a badge of honor. Surely configuring your equipment to be as efficient as possible in this environment will provide major benefits, and it does.

Balance… (Photo: Steve Davis)


Trim refers to the forward to back orientation of a diver, usually referenced as ‘in trim’, ‘head down’ or ‘feet down’. Correct trim is a basic diving requirement to move efficiently through the water. Good trim is a function of correct weighting, positioning of this weight on your body, and the positioning of gas in your BCD and dry suit.

While good trim can also be achieved in backmount diving, correct trim is a hallmark of a competent sidemount diver. This is primarily due to the pro-trim effect of having your cylinders at the sides of your body allowing them to more closely align to your centre of gravity and your buoyancy.


Photo: Aire Eder

With your cylinders sidemounted, they are on either side of your torso. So regardless of your orientation your centre of gravity and your buoyancy are always near the centre of your body. Turn onto either side, upside down, inverted, upright, it doesn’t matter, you remain balanced.


Stability is a function of trim, balance and buoyancy control. Being stable means being able to relax almost completely and to stay in trim and balance. This is the resultant state when the force of gravity is completely balanced by your buoyancy while in trim. You are truly weightless but more than that, you are a stable platform, and you can a whole range of tasks or skills while holding your position in the water column.

Streamlining for efficient movement through the water. (Photo: Steve Davis)

This is important when applying sidemount diving to overhead environments such as caves or wrecks where contact with the cave or wreck floor can cause a loss of visibility due to silt. It is also required for decompression diving where you need to be able to hold decompression stops and perform tasks such as gas switches while holding a specific depth.

Tight spaces, again… (Photo: Brian Hadfield)

Two independent gas supplies… (Photo: Brian Hadfield)

Stability, buoyancy and control… (Photo: Audrey Cudel)

Good stability is not the sole domain of sidemount – skilled backmount divers can achieve the same result but I would maintain it is easier to develop this skill in sidemount than backmount.


In addition to carrying more gas, one of the key reasons for diving with two or more cylinders is redundancy.

Redundancy is a mandatory requirement for any type of technical diving since it provides additional safety in the event of an equipment failure or diver mistake.

Easy access to valves… (Photo: Steve Davis)

All multi-cylinder configurations provide this redundancy in terms of both cylinders and regulators but sidemounting provides two truly independent gas supplies as opposed to one separated by an isolation valve. This facility has pros and cons but it is comforting to know you always have at lest 50% of your available gas protected in the event of a failure.


Another key difference is the location of your tank’s valves and regulators. In sidemount your cylinder valves are in front of your body, under your armpits. The valves for a backmount twinset are out-ofview behind your head and shoulders. Many backmount divers can struggle to reach their valves, especially when in a dry suit with thick undergarments. In sidemount, it is many times easier and faster to isolate an issue by closing a valve and switching regulators.

Photo: Aire Eder


Managing each cylinder individually both in and out of the water means sidemount is easier for those with back or shoulder issues or those who struggle with the weight of backmounted doubles. Subject to water conditions and the diver’s requirements, a sidemount diver has the option to don and doff cylinders on the boat, or to do so in the water. This flexibility is a large advantage for those that might struggle to handle a twinset but otherwise could perform two-cylinder dives.

Putting all these factors together: streamlining, trim, balance, stability, redundancy, access to valves, and managing equipment – and I feel the case for diving sidemount is absolutely compelling.

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