On holiday in Spain and doing the usual diving from RIBs in warm, clear Mediterranean water with lots of life. Lovely diving, but wanted something more challenging so I took the opportunity to do a sidemount course. The course was run by an experienced sidemount instructor and cave diver (some great caves around the Costa Blanca, particularly Moraig which is listed in Martyn Farr's book Classic Darksite Diving... I digress). My objective was to find out what the sidemounters keep chirping on about. So basic config, trim, protocols, etc. I also want to know how to use stages as deco is a major part of my diving these days. First (short) day was getting used to the kit and a 'getting used to it' dive. Diving in a Techline sidemount harness with 5kg of lead, in my drysuit with simple undersuit (bloody warm on the surface!) What an amazing experience. The rig just flattens you in the water, completely flat trim with zero effort. You can turn sideways on and stay there. Similarly tilt head down and remain there, ok, you do need to be aware of air in your suit migrating to your feet. It's amazing to not have that bloody great keel weight on your back in the form of a twinset or single tank which needs the wing to wrap around it to compensate. Really amazed at just how easy it was to remain flat and totally still in the water. Sure, I'm pretty OK with a twinset, but they're a complete sod when you're tipping sideways if you're squeezing through a gap. Similarly a twinset is a total bastard when going head down: most definitely not stable and wants to tip you head over heels. Messing around I even swam upside down without budging in buoyancy. The big difference between sidemount and backmount is having to 'manually' manage your gas, swapping between the cylinders every 30 bar. And remembering which tin you're breathing from! Not that onerous with a bit of practice. Getting used to donning one's kit isn't that hard. Left cylinder first, back clip on, bungee around the valve, hose around the neck and on with the necklace bungee. Then right cylinder which has the longhose partially stowed on the cylinder bands, back clip, then bungee around the valve, hose around the neck like backmount and reg clipped off if not breathing from it. The gauges are on 15cm hoses and left sitting on the cylinder. The next (short) day was running through the skills. Out of gas donation - standard longhose donate protocol although you may need to unclip it if you're breathing from the backup (left cylinder). Mildly irksome re-stowing the longhose as the cylinder is steel and is very tight in to your chest, so remove the bungee from the valve and let the stage drop down and stuff the hose back. Not hard, but a bit of practice needed. Valve drills are dead easy. The valve are right in front of you, no "muscle memory" and endless practice required like backmount. Just shut the thing down and breathe it down and switch to the other reg. then open up, purge, then repeat for the other side. Jumping ahead to day three with the stages, I had an issue with the stage where the reg had become dislodged and was blowing gas out of the NIN connector; no confusion - you can see the offending reg, and unlike backmount, I could see the other three cylinders and all regulators. Other skills included feathering the valves to breathe from a free flowing regulator (simulated by holding the purge down). Wow, so sodding easy as the valve is in front of you and none of that reaching behind your head. To be fair, backmount has a manifold so you'd just shut down the offending post and breathe the gas from the other reg --n sidemount you need to learn how to feather the valve (close and open) as you may need to access the gas in that cylinder if in an overhead environment or deco, etc. The big benefit of sidemount is you've nothing on your back, just a very streamlined bladder. But you're wider with the cylinders under your arms. So if you've a tight squeeze to get through you can bring one or both cylinders forward by unclipping the cylinders from your hip D rings and rotating them in front of you. Being heavy steel cylinders, this does affect your centre of gravity, but it's still a trick that you can't do on backmount. Kitting and dekitting on the boat and in the water's really not an issue. Just remember it's left on first and right off first to stop the hoses tangling. Steel cylinders are heavy, so be careful not to drop them into Neptune's locker. Quite frankly it's a doddle on a RIB. Massively easier than diving with a twinset off a RIB. Day three was running through the kit configuration in more detail. Some subtle differences between normal stage configurations, mostly down to the way that the bungees pull the nose in and the hip clip twists the stage. Also the cylinders need to be adjusted to fit the diver, measuring from the armpit to the hip, the lower cylinder clip may need to be adjusted up and down to match. Some other adjustments for steel vs aluminium to compensate for their floatyness. Then the practical dive which we took a couple of stages for me to rig up. Again a doddle once shown the best way: clip the hip clip first, then kick the stage under the sidemount cylinder, and clip the valve clip onto your chest D ring; reverse for unclipping, nose, kick under and around the back. No difference with stage switching "no-tox" protocols: you watch me switch to this stage with this MOD... The whole stage session was done in the sea at 4 metres. The sidemount rig is so intrinsically stable that there just aren't any issues with your buoyancy as you're throwing stages around. At the end of this session I was left asking the instructor "is that it?" It really was that simple. So, pay for the cert or not? I didn't do it for yet another card, but for the knowledge of using sidemount. Arrrgh... ok, I paid for the cert. Now a Tech Sidemount Diver. I was utterly amazed at how stable and simple the sidemount configuration is. It's pretty simple although there's a lot of subtle gotchas, but that's what the training's for. As someone who's getting older, I really appreciate having two separate cylinders to lug around rather than a massively heavy and awkward twinset that's an utter bastard to lift into the car boot, let around carry into the gas room. I'm now wondering why sidemount isn't more popular. From what I've seen it's a much better tool for the job than backmount is. Sure, when there's any restrictions/squeezes sidemount is the tool and backmount is a liability. For general purpose diving where redundancy is necessary, it's definitely a great tool for the job, certainly equal to backmount. Of course the thought of 12 sidemounters all kitting up at the same time on a hard boat might favour the backmounters. Will be getting a sidemount harness in the near future. Plenty of practice and kit fettling required though. Would definitely recommend sidemount. Have seen the light.