The following commentary was first published as a post on the Scubaboard internet discussion forum. I felt that it provided a very beneficial perspective on the positive and negative aspects of sidemount configuration; particularly in comparison with back-mounted alternatives.  It’s a useful read for those divers, of all levels and backgrounds, who are considering their interest in this alternative approach to scuba configuration…   Andy Davis


Technical Sidemount Diving

Sidemount – Thoughts For Those Interested In Trying It

by Kevin Bennett, British Columbia, Canada.

I’ve noticed quite a bit of traffic on this forum about sidemount, and seen some strongly held opinions written against it, by divers that have not actually dived using this approach, so I thought I’d post my own experiences, good and bad, for those that are thinking of taking up sidemount, but are confused by the “noise” that seems to surround this style of diving.

To give you some background, I’m a moderately experienced diver, with about 400 dives under my belt, undertaken in a number of settings. I’ve dived drysuits in the cold waters of the UK and Canada, shorties in the warm waters of Hawaii, Turkey & Mexico, done long decompression dives in Bali, bimbled along in the Maldives and been swept along by the currents of the Kimodo islands. My first certification was in 1984 through BSAC, I have a mittful from PADI taking me up through Advanced Open Water, Nitrox, Rescue and Tech50. My last certification is as Full Cave Diver through TDI.

I have no association or attachment to any of these or any other training association, except to say I found BSAC and TDI’s training to be superior than PADI. PADI have very good materials, but I found the quality of their instructors to be quite low (just my experience, others clearly have had better instructors).

I started sidemount diving immediately after my Tec40 certification because I could not stand back mounted twins. I found them heavy, awkward and required me to dislocate my shoulder to perform valve shutdowns. They are, as the joke goes, like swimming with a refrigerator on your back.

The more I dived with backmount, the more unsafe I felt with them. The rig I was using had no quick release buckles, so it was a bitch to get in and out of, especially with in-water recoveries to a boat, and I came to believe that in an emergency I could not easily ditch it.

I did a few wreck dives and hated the lack of balance and the inability to get into (or, more accurately OUT OF) tight spaces and I never felt that I would be able to perform a valve shutdown in a tight space or be able to shed the rig if I got stuck.

By comparison, in sidemount, you have two totally independent gas supplies, the valves are easy to get to, you can do your own bubble checks and, in the case of a catastrophic failure, you can either feather-breathe (turn the valve on and off every time you take a breath) to consume as much of the gas in the faulty tank as possible, or simply switch to the other regulator. It’s a self-contained, redundant breathing system, and you can easily remove one or both tanks, or the whole rig if you get caught on anything.

In short, I came to believe that diving backmount was, for me, unpleasant at best and dangerous at worst and that sidemount is more flexible and far safer.

Sidemount diving is not without its challenges though.

You have to get used to swapping your regulator underwater every 15 minutes, so you draw down your gas supplies evenly, keeping your trim balanced, and maintaining a safe gas reserve. There is no point breathing all the gas from one cylinder, forcing you to dive lopsided, and then having a failure on the full cylinder. You breathe equally from both and manage your gas supply. You get used to this very quickly.

By far the bigger challenge is rig set up. Sidemount is FINICKY! You will spend a lot of time getting your rig configured just the way you want it. . Moving the lower tank clip a mere ½” can make the difference between a balanced and an unbalance rig. The port you use for each hose makes a difference; I found that mounting the SPG on a 6” hose pointing upwards, like a lobsters eye on a stalk was the way to go in open water, but NOT the right way for wrecks or caves, where the SPG catches on every damn thing. In that environment you want them pointing down, flush with the tank, or tied to the first stage.

The other thing is that sidemount diving in caves is not the same as sidemount in open water.

In open water, I didn’t feel a need to have the tanks tightly strapped to my body, because, for the most part, you’re not particularly active in the water, so streamlining is not as crucial. It’s not unimportant, but the ability to clip tanks to yourself while on the boat is certainly more important, because you can then back roll entry and start swimming, instead of fussing around clipping tanks to yourself in the water. And anyway, with four tanks you have the streamlined profile of a Quonset hut and you’re going wherever the sea wants you to go.

In caves though, you are far more active; constantly shifting your body over, under & around obstacles, and through restrictions, orienting yourself on your sides, back and vertical frequently. In this situation you need the tanks to be glued to you, and as much a part of your body as they can be. You need to know exactly what your profile is underwater, so you can judge how to fit through restrictions. You can’t do that unless you have a static profile.

I strongly urge you get instruction from a sidemount instructor, or, failing that, a friend with experience; you will be a lot less frustrated. Sidemount is not one-size-fits-all like single or twins, and it takes time to get it to fit you exactly.

I believe that sidemount will become the norm for divers that move beyond PADI Open Water certification, and I see it as a big leap forward for the diving industry. Dives will be longer; double the air is double the time, or deeper, as people explore TecRec. Shops will be able to sell more training and more gear, adding much needed revenues. Diving will become more interesting. Beginner divers have so little awareness of the depth of the sport, and learning more equipment and more technique will hold their interest for longer.

I see a lot of talk about sidemount not being DIR, which tells me that DIR needs to update its standards, otherwise it’s an obsolete doctrine. Certainly the local guides here in the Yucatan were very scathing of GUE restricting their students to backmount only. There was not a single cave instructor I dived with or talked to that did not prefer sidemount. Of the 60 or so other divers I saw, only three were wearing backmounts, and they said they were going to switch. I’ll add to that and say that, even as a new cave diver, I was able to dive in parts of the caves that were inaccessible to twinsets, but easy as pie for sidemount. Restricting yourself to just the wide passages makes no sense to me when there is a way to safely dive in tighter spots; it’s the difference between driving on a highway and taking a mountain bike off road.

I’ll now switch from a general view to the specifics of my rigs.

For open water I use a DiveRite Nomad EXP and love it. Easy to don and doff, I easily manage four tanks, and it has buoyancy for more. It’s a heavy rig, coming in at around 12lbs, so it’s hefty to lug around airports, but wearing a shortie, I don’t need any weights. (I’m 49, 5’10”, 200lbs, stocky and could eat a few less cheeseburgers, but I’m not obese). I like the ring bungie system as it’s very easy to clip tanks to you on the boat and the backplate system is flexible enough that you can back mount a single or twinset if you wish.

For divers looking to move into open water sidemount, this is one of the many good rig choices you have available, and I have no hesitation in recommending it.

For cave diving I chose the new DiveRite Cave LT for no other reason than I’ve always been satisfied with their gear and the LT was quite a bit less money than the equivalent Hollis SMS50.

Sidemount in a cave is not the same animal as sidemount in open water though, and I have to say I struggled with the LT for a long time, before I got familiar enough to modify it to suit me better.

The LT comes with ring bungies, the same as the EXP, so I thought they would work the same way. After three cave instructors tried to get them to work, over the course of 10 dives, I threw away the ring bungies. They did not keep the tank tight to my body.

Instead, I loop a bungie from the top of the backplate, around the valve stem, causing the tank to be pulled backwards and to roll inwards. This puts pressure on the lower tank clip, effectively locking it in place and keeping the valves under your armpits.

The rolling action presses the tanks against your sides, keeping them firmly against your ribs. When you move, you move as a single unit, with a consistent profile. Your propulsion is not reduced by the momentum of your tanks dragging and then catching up with you, like a weight on an elastic.

The other thing I did was throw away the puller on the lower dump valve. The stock one is the size of a cherry and far too small. You use the lower dump constantly in caves, because the cave depths change as you swim. The cherry got lost among the reels and other crap that gets hung on the butt plate and floats around behind you. I switched it for a larger bell shaped puller and it became much easier to find.

I will be swapping out the rails on the butt plate too, because they have a sharp 90 degree bend. You carry a lot of stuff on the buttplate, attached by double ended clips, and these constantly get jammed, and occasionally open on their own. I lost two $40 reels this way. I’ll be replacing the bent rails with straight rails.

I was, and remain, disappointed with DiveRite manuals, which are useless and only tell you how to clean the unit and that diving is dangerous. Well, thanks for that! They tell you nothing about how the ring bungies are supposed to work, how to set up the chokers, how to rig the tanks and all the other stuff you need to know to get the rig set up properly. That’s just scientific wild ass guesswork until you get something that works for you.

Other than that, the rig suits me, I’m just less hesitant to recommend it though and you should try a couple of different rigs if you can. The Hollis seems nice, as do the X-Deep, UDT and Razor systems. Each have their own quirks and you should find the one whose quirks you can live with.

I would encourage any diver to try sidemount. It extends your range, doubles your bottom time and it’s very comfortable. I think it’s safer than twinsets, you’re more self-reliant, it is more comfortable in the water, it’s more comfortable out of the water and you can reduce wear and tear on your body by carrying one tank at a time.

You will most likely require training though, because it is finicky.

So, that’s my two cents. I’m by no means an expert and love to learn better ways to do things. I’d love there to be DIR standards for sidemount, as I think DIR is a good thing, provided it is education, technique and configuration based, rather than blindly restricted to specific gear. That to me is not standardization, it is ritualization. Rituals are a poor substitute for understanding, and abdicate responsibility for good, in-water decision-making. If we are following good standards and have good training I can dive in a blue wetsuit, and you can dive in a red drysuit, and we can still both be safe.