Over the last week, I have been doing a side mount diving course with Phil the Tech instructor at Cebu Dive Centre with 
To be honest I have been diving side-mount for a year or two but mostly on a recreational level for liveaboard holidays. The main reason for doing the course started off because after 8 months in Moalboal and most of that in lockdown I was getting bored, add to that my tech skills are getting a bit rusty, and I fancied a bit of a challenge. And proper tech courses are certainly challenging.
So what's side-mount you ask. Well, it's pretty much what it sez on the tin. Rather than conventual SCUBA with a single tank on your back side-mount consists of rigging one or more cylinders along the side of your body. It was first developed in the UK with cave diving as it makes getting through restrictions easier and carrying tanks in the dry sections is simpler than lugging twin tanks. Not me in the photo BTW
The equipment is a little different than normal recreational SCUBA. The buoyancy device is a bit simpler as it doesn't need to support the tank but has bungees to hold the cylinder valves and few more D rings to attach the bottom of the cylinder and any other gear you might want to carry.
The cylinders themselves are conventional SCUBA cylinders and maybe of any size to match the dive, S80 11 ltr is quite common but smaller divers often find S40 or 7 ltr tanks easier to deal with. What does change is the way they are rigged. Each cylinder will only have one regulator attached and a pressure gauge on a short hose. There are also clips to attach the cylinder to the harness, with rubber bands around the tank to keep all the hoses tidy.
Why dive side-mount.
One of the big advantages of tech diving side mount over back-mounted twins is you have the cylinders and first stages in front of you all the time so its a lot quicker and easier to see if you have a leak or you're losing gas, and it's also much easier to isolate a regulator in event of a free flow. On my first dive on the course my instructor had an HP pressure gauge hose leak, with side-mount it was quickly spotted and the cylinder shut to save the gas, this would have been a pain with back mounted twins.
If you're getting on a bit like me it's a lot easier carrying single tanks around and kitting up in the water. S80 back-mounted twins, deco stage cylinder with a backplate, and harness is probably close to 50kg that's a lot to lug around on a moving boat. As single cylinders weigh around 15 kg each so much easier. For anyone with back issues or getting on a bit, side-mount makes a lot of sense.
Diving side-mount in overhead environments like wrecks and caves makes a lot of sense too, the cylinder valves are less exposed, trim is a lot easier and you're able to swing the cylinders in front to reduce your profile even smaller if you need to swim through small gaps.
Some different skills are involved mostly around cylinder handling and trim but Phil was quite good with this old dog. The one-handed mask floods and no mask out of air swims were not so much fun for me but I'm sure they were amusing to watch.
Cylinders are all ready for the last dive of the course which will be a 50m decompression dive with 32% nitrox to accelerate the decompression.
One advantage of diving deeper you sometimes see things recreational divers don't. In this case an eagle ray at just over 40m.
Oh and the course? Yes, I did pass.
All for now Hivers it is time for another dive.