A diver reaches back to open the cylinder-valve. The left hand is under water, pushing the cylinder up to make the manoeuvre easier
Trials & Tribulations Pt 2
DO YOU REMEMBER HAVING TO DO the mask-flood and mask-removal and replacement drills during your beginners’ course? How could you ever forget, right?
Do you remember hating them and thinking afterwards: “Thank goodness that’s over, I’ll never have to do that again.”? Or perhaps you’re one of the fortunate ones who had all sorts of difficulty doing the drill, and finally managed it one time only so that the busy instructor could tick that box on his checklist and move the group on?
Well, this message is especially for you! There was a serious purpose to those drills. They were not devised just to give you a hard time.
1 BROKEN MASK-STRAP
On any dive your mask-strap could snap or your buddy’s wild fin-kick could separate you from your face-furniture with one blow.
You might catch your mask as it flies off, but chances are that it’s gone. This in itself is not a serious problem; you will be visually impaired but can still look around you, gather your thoughts, signal for assistance if you wish and see which way is up so that you can make a slow, careful ascent to the surface, breathing from your regulator as normal and remembering not to inhale through your nose, which is now exposed to the water.
Losing your mask will not kill you but panicking when you lose it just might! Losing control of yourself when it happens and bolting to the surface could have tragic consequences.
So you need to be certain you won’t panic if you lose your mask. How do you do that? Practise, practise, practise.
In a pool or during a dive with a buddy in shallow water, remove your mask and then swim along for a few minutes, remaining calm.
Can you see the readings on your watch, computer or depth and pressure gauges without your mask? Do you notice how the design of your regulator second stage diverts your bubbles away from your nose and eyes? See how easy this is?
If the possibility of losing your mask really bothers you, or if you don’t want to allow the loss of your mask to interrupt a dive, do what many technical divers do to guard against the inconvenience of having to complete long decompressions without a mask.
Invest in a frameless back-up mask that will stow neatly in a pouch or BC pocket.
Make sure it’s stored so that you can access and deploy it quickly in an emergency, and practise fitting it and clearing it under water until the action becomes instinctive.
2 LOOSE WEIGHT-BELT (LOST WEIGHT-BELT)
There are two issues here. Your primary concern is to ensure that your weight-belt does not fall off during a dive. Hold onto it at the buckle every time you enter the water and check that the buckle is still tight and the belt correctly positioned around your waist before descending.
As you descend the increasing pressure at depth will compress the neoprene in your wetsuit and your belt will become a little looser. So remember to reach down and tighten it once you arrive at depth.
Of course, having done this you might find that the belt becomes a little tight when you return to the shallows. If so, just relax the buckle again.
The second issue is the risk of a runaway ascent in the event that your weight-belt comes off.
To minimise the danger this presents, you can do three things.
First, buy a BC with minimal integral buoyancy. That means one that will give you sufficient buoyancy on the surface when you inflate it but, when deflated, doesn’t require too much weight to get it under water.
Second, practise dumping all the air from your BC quickly in an emergency. Know where the dumps are and which body position you need to be in to make sure no air is trapped. Avoid complex jackets with huge wraparound air-cells.
Third, carry only as much weight as you need!
3 BC FAILURE
BCs are highly reliable but they can fail in a couple of ways that you may not have considered.
The first of these is that they can start auto-inflating. It is a great advantage to be able to add air directly from the cylinder via the low-pressure inflator hose, but the valve at the BC end can corrode and fail, allowing air to seep into the BC and increase its (and your) positive buoyancy.
It’s a sign that this is happening if you find yourself constantly having to dump air when you haven’t added any.
You can keep the valve corrosion-free by wiping it clean every now and then with a little white vinegar on a cotton bud. If the valve is already corroded it may be too late for vinegar, but your local dive-centre should be able to replace it.
However, if you have not noticed the problem or are using rented equipment and the valve suddenly fails explosively, you will need to have the presence of mind and dexterity to disconnect the hose under water, dump the air and then inflate the BC orally when you get to the surface.
These skills are introduced in most beginners’ courses and they should be practised and maintained, as they have real purpose.
Shocking as it may be to contemplate, you also need to be prepared for your BC to stop functioning as a flotation device. The material with which these devices are made is tough and hard to pierce, but it can wear or tear.
The real potential failure points, however, are the dump-valves, which are made of fairly brittle plastic that cracks easily. Scuba equipment is often handled roughly in transit, and heavy cylinders fall on top of BCs all the time. The cracks are often difficult to see, and the first sign of a problem is usually bubbles escaping from the fitting.
However, sometimes there is no warning: I have seen an apparently good shoulder-dump valve shear off completely when the BC was inflated under water.
If this happens, the BC immediately becomes useless and the dive is over.
Dump at least part of the weight you are carrying in order to swim to the surface and, once you get there, dump all your weight to stay buoyant.
4 ROLLING INTO THE DEEP WITHOUT AIR
The history of diver-training is based on people assessing the causes of accidents and then designing courses to try to ensure that they are not repeated.
This is all very reassuring but this consistent approach also means that the writers of new course texts tend to add new techniques and new technologies to what has gone before, but are very reluctant to omit the older material.
This leaves us with some historical anomalies, and one of these is the advice given to all new divers that they should open the cylinder-valve all the way and then twist it back a quarter- or a half-turn.
This advice dates back to the mid-20th century when our sport was in its infancy, and it was feared that valves could be damaged if left open all the way.
Today, once your cylinder valve has been opened the only thing you can achieve by twisting the valve back is to partially close it again.
Also to blame for a number of incidents in which a diver has inadvertently entered the water with the cylinder-valve closed or only a fraction open is the over-attentive diving partner with poor plumbing skills who misguidedly closes an open valve while performing a buddy-check.
Here is how to make sure you never enter the water with your cylinder-valve closed, even partially.
Forget what you were told in your training. Turn your valve all the way on before you put your scuba gear on. Then do not let anyone else touch the valve after that, no matter how much your buddy insists or what exalted rank they hold in the dive industry.
Before you enter the water, take four breaths from your regulator and watch your high pressure gauge while you do so. If the needle moves when you breathe, your valve is either fully closed or almost closed. Why four breaths? Because you might not be watching your gauge, and if your valve has been opened then closed again, it will take you four breaths to clear the hose. That horrible empty sucking feeling will come on the back of the fourth breath.
Unless the dive-site conditions demand it, never enter the water negatively buoyant. On the rare occasions that the dive-site conditions require you to go in negative and plummet, know how to open your own cylinder-valve if you suddenly find yourself with a vacuum in your regulator as you descend.
The usual technique is to reach down and behind you with your left hand and push the base of your cylinder upwards. Then reach behind your neck with your right hand, grasp the valve firmly and turn it away from you.
Don’t place blind faith in your high-pressure gauge. The vast majority are cheap mechanical devices with cheap components.
They can malfunction and mislead. Many have no actual zero reading; they just have a series of red dots below the 50-bar mark that become smaller until they peter out.
Often there is a registered trademark symbol (a circle with an R inside) below the point where the dots run out, and you may think this is the zero. It isn’t! When a gauge starts to fail, the needle never actually points at zero.
Look closely at your gauge when it is not attached to a cylinder, and make sure you know where the needle will be when you have no air remaining!
Read more from Simon Pridmore in:
Scuba Confidential – An Insider’s Guide to Becoming a Better Diver
Scuba Professional – Insights into Sport Diver Training & Operations
Scuba Fundamentals – Start Diving the Right Way
All are available on Amazon in a variety of formats.