Another vital piece of equipment that every diver needs is a contents gauge (Submersible Pressure Gauge - SPG)

Most people learned to dive with a console that contained the SPG, a compass & perhaps a computer or depth gauge as well. Whilst this seems a good idea superficially (keep all those handy things in one place), it does have some serious drawbacks:

They are large, cumbersome and get in the way and drag along the bottom or catch on wrecks. How often have you seen a console get dragged along - diving in silty overhead environments with such consoles stirs up silt – only to be nowhere to be seen when the diver wishes to check how much gas they have remaining.

The computer is better suited to being on the wrist where it can easily be read and protected from banging against anything. All you need is the SPG itself, the compass is better on the wrist (navigation is actually easier and more accurate this way too because you are free to hold the compass where you like (up to eye and straight in front of you). The depth gauge is part of your computer and thus is wrist-mounted.

SPGs should be well made and glass faced - plastic is not as good as on deep dives as they flex & make the needle stick and plastics can scratch as well making the gauge harder to read. A brass case resists the water pressure at all depths better and so the gauge tends to be more accurate than the plastic cased SPG’s. Try to find one with clear numbering, a brass case and, if possible, a mineral glass face. The Halcyon SPG is perfect.

The High Pressure hose that you normally see in shops is in the region of 36 inches long which is excessive. Ideally the HP hose should be 24 inches long and clipped off to the left near the left hip using a large stainless steel bolt snap. Here the SPG & HP hose is streamlined, it won’t dangle and it is protected. Practice is needed so that you can quickly unclip it when needed. The boltsnap should be tied on with cave line.

To make the console swivel you need a small swivel pin with 2 tiny O-rings at each end. These O-rings can gradually wear if grit and sand gets into the connection and is left there for some time. Each turn of the swivel can gradually wear them thin.

If you were to experience a leak from this swivel connection, you would notice it sooner without a rubber console as the console or boot obscures the joint. Don’t worry about it being vulnerable - a contents gauge protected by a rubber console bashing into things is far more vulnerable.

A well fitting harness should be adjusted so that it is not really tight (you need to be able to get out of it easily) but not so loose that the set rolls around on your back which would be really uncomfortable.  I’ve drafted out some instructions to help you get it right for you.

A diver's harness should be rigged from one piece of webbing and should have no quick-release buckles or other failure points. Though plastic quick-release buckles seem to simplify the process of getting into and out of one's dive gear, these “savings” are illusory, putting a diver at greater risk that s/he would be without it. In many cases this could prove fatal as the diver clings to tanks whose negative tendency stands in stark contrast to his/her own positive tendency. In cases where the loosened or dislodged quick release does not cause a diver to lose their tanks it can easily cause a dangerously significant shift in weight, throwing the diver off balance.

To get your harness to fit well, wear your dry suit and under suit just as you would when diving.  I start with the shoulder straps.  Put the harness on your shoulders without doing up the waist or crotch strap. Reach back and see if you can touch the top of the back plate – as in the picture to the right.  A friend will be able to tell you if you are in the right area as sometimes we reach into the channel of the plate and think that we are missing it.  The plate tends to end up roughly where a rear entry dry suit zip would be – perhaps a little higher depending on your reach.

When you are happy with this, take the plate off and check that the shoulder straps are of equal length as in the first photograph.

Next, do up the waist strap.  The waist strap should go straight across from wherever the holes in the plate are on your body – don’t drag it down to where your waist really is – we are all different heights and some very tall people will find that it is over their chest rather than near their waist.  For this reason, it shouldn't be too tight and it should never restrict your breathing.

Now the waist strap is in place, reach th rough your legs and bring up the crotch strap to check its length.

The crotch strap is also one piece, and has a loop in the front through which the waist belt is threaded. The crotch strap is needed to hold the diving system in place and to prevent it from sliding up toward the head when entering the water or when inverting; later it will also be necessary for any diving involving a diver propulsion vehicle (DPV). Once threaded through the crotch strap, the belt buckle should be placed to the right of center so as not to get accidentally opened by the crotch strap.2  The crotch strap is there to steady the rig, not to drag the waist down into the wrong position.  A centimetre or so longer than necessary will allow easy access and removal of the strap in use.

To avoid the unnecessary clutter of multiple attachments, the DIR harness only supports one D-ring on each side of the chest, one D-ring on the diver's left hip and two D-rings on the crotch strap. The chest D-rings should be bent slightly so that only one hand is needed to clip bottles to them. The hip D-ring is used for pressure gauges, stage bottles, and other gear, while the crotch strap D-rings are used for DPV attachment (front) and towing (see above). Individuals should not clip equipment to the front D-ring, because it will hang too low and will create entanglements and drag; divers should clip off any additional gear that is being towed to the rear crotch strap D-ring.

The shoulder D-rings should be positioned relatively high on the shoulder straps, especially if you plan to utilize stage bottles in your diving. If the D-rings are too low, the stage bottles will hang too far away from your body, causing significant drag and possibly damaging marine environments.

The shoulder D-rings should also be high enough to allow for proper storage of your Scout back-up lights and to allow for ease of use of your wing’s inflator hose to adjust trim and buoyancy, yet not so high that you can’t clip an item off with the same side hand as the clip.  Find out where the shoulder D rings should be by extending your arms when your eyes are closed. Bring in your thumbs and where they naturally fall is where the tri glides for the D rings should be.

The waist D-ring is used for clipping off the SPG and for stage bottles. To position the waist D-ring, run your left thumb straight down your left side until it hits the waist strap roughly in the centre of your body. Your thumb should intersect the D-ring, very close to your hip bone.   If you habitually use a lot of stages and leashes this may have to be moved back slightly

The front crotch D-ring is only used with a tow-behind scooter. Gear should never be clipped to this D-ring, as it will hang in the slipstream and pose significant entanglement hazards. The back D ring should be worn where you can reach it taking into account the length of your tanks.

Remember, while standing on land, your harness should be snug but not uncomfortably tight. In the water your harness should be snug enough to prevent notable motion of the cylinder as you change orientation, but not too tight so as to bind or restrict your complete range of shoulder and arm movement.

During certain diving scenarios it becomes desirable to clip the light head such that the beam points down away from a team member’s eyes. In order to facilitate this need while reducing the complexity of multiple clips GUE procedures utilize the placement of a permanent clip on the handle of the light head and a loop at the rear of the light head. The rear loop allows the diver to temporarily clip a double end clip to the beck of the light head. I've been asked a few times how I tie the loop and thought it would be helpful to show the process.   

Start with a piece on bungy cord which is rigid enough to make a loop which will not bend.   Tie a simple overhand knot in each end. Form a loop with this bungy - just loosely wound round in a circle - you are not going to tie it in a knot.  Take some cave line and wrap it around the end of the ballast where the light meets the cord, over the bungy loop.  It is tricky at this point to keep it all neat and tight - but the tighter you can make the cave line the better the result will be. 

I build up three wraps, trying to get the line to lie neatly round the ballast.  At this point the bungy loop is not pulled tight so it is smaller than it will be when finished. 

Then I tie a simple overhand knot on one side of the loop, cross over the ends to the other side and tie again - as tight as I can.  This helps keep the finished loop perpendicular to the ballast which makes clipping off easier.

When I am content that this is OK, I cut the ends of the cave line and burn them to melt the ends into the knot.  I can then take some pliers or strong fingers and pull the bungy loop out so that the end knots snug down on the cave line holding it all in place and giving me a loop big enough to clip into easily and quickly.

No skill presents more of a hurdle to new divers than mask clearing and removal, and a way of learning to do this quickly employed by most recreational agencies is to learn with a physical reference throughout - kneeling on the bottom whilst negatively buoyant is the common way to learn.

It may be quicker to teach the fundamental skill in this way but it has serious repercussions. If a mask is accidentally dislodged it is unlikely that a diver will be anywhere where a physical reference exists. If there is no underlying buoyancy control then the diver is immediately at risk of ascending or descending during their efforts to replace their mask and, sadly, there have been serious accidents where this has happened.

Mask clearing/replacement should be practiced neutrally buoyant so as to prepare the diver for the unexpected loss of vision which will occur if a mask is dislodged. Practicing shallow in open water or in a swimming pool is not only safer but, given the buoyancy swing is greater in shallow depths, it is a skill which is harder to master shallow.

The first 6 metres is a great place to practice. Before you remove your mask, take a moment to check that you are indeed neutral and that your breathing is stable and on the centre of your lungs (see buoyancy in the skills section). When you remove your mask, be aware that it is an instinctive reaction to breathe more deeply if cold water hits your face, so prepare for this and seek to try to maintain the same breathing pattern as before. Using a low profile mask means that it will clear very efficiently with very little effort, and with very little air from the lungs.

Feel your buoyancy, suit, ears and light all give feedback – but don’t be conned into a false reaction – it’s amazing how our mind can play tricks on us. If you were neutral before you removed your mask and you maintain your breathing you will not move in the water column. Replacing a mask need not be a one handed job – use two if necessary.