Safe Diving Practice and Problem Solving Part 2 – Gas is Time, Effective Planning

Any problem is solvable with enough time, and in diving Gas (Air) is time. As long as you are breathing you can deal with what is going on. There are 2 aspects to ensure you have enough gas for any situation:

• ·         Gas Planning and Management
• ·         Emergency Procedures and Redundancy

Let’s first explore as Planning and Management. During this blog I use Gas which maybe Air, Nitrox or Trimix depending on the dive you are planning. Firstly Gas Planning. It is important to be sure that you have planned a dive that is actually possible to do. Many divers do dives that I class as ‘Suck it and see dives’, where you dive until you reach a set bar level. This is ok for shallow dives and with greater experience you can start to judge how much you breathe on any particular type of dive. However if you want a more accurate method then you can employ a technical diving method.

First you need to know how much gas you have, and with the metric system it is nice and easy.

Liters of Gas (ltr) = Cylinder Capacity (ltr) x Cylinder Pressure (bar)

For example a full 12 ltr cylinder at 230 bar

Liters of Gas (ltr) = 12 ltr x 230 bar

Liters of Gas (ltr) = 2760 ltr

The next stage is to know how much you breath, this is known as you Surface Air Consumption (SAC). To work this out accurately swim at a constant depth for 10 min and measure how much you breathe in bar and then convert this to how much you breathe at the surface:

SAC = (Pressure of Gas Breathed (bar) x Cylinder Capacity (ltr)) / (Time (min) x Pressure of Depth (bar))

For example you swim at a steady pace at 20m for 10 min and breathe 20 bar of air from a 12 ltr cylinder:

SAC = (20 bar x 12 ltr) / (10 min x 3 bar)

SAC = 240 / 30 = 8 ltr/min

Another way to calculate a quick average SAC is to take the average dive depth from your computer and use the total gas pressure used through the whole dive and the total dive time.

For example your average depth is 15.5m and the dive was 40min. In that time you breathed 80 bar from twin 12 ltr cylinders (24 ltrs total):

Avg. SAC =( 80 bar x 24 ltrs) / (40 min x 2.55 bar)

Avg. SAC =1920 / 102 = 18.8 ltr/min

Now you know how much gas you have and how much you breathe you can work out how long you can dive with redundancy gas left for emergencies. In Tech diving we use the rule of thirds: 1 third to dive away from the entry point, 1 third to get to the exit point and 1 third in reserve for emergencies.  In No Decompression diving people tend to plan to leave around 50 bar in the cylinder at the end of the dive. Whatever safety margin you decide it should reflect the type of dive that you are on. Here is how to calculate how much time you have on a dive. First work out how much gas you have and the amount of safety margin you want and then divide the useable gas by your SAC at depth.

For example you have a 12 ltr cylinder with 230 bar and you are planning a 20m dive and you know your SAC is 18 ltr/min. You want to end the dive with 60 bar how long can you dive for.

Cylinder Capacity = 230 bar x 12 ltr = 2760 ltr

Safety Margin = 1 – (Reserve Gas Pressure / Start Gas Pressure)

Safety Margin = 1 – (60 / 230) = 0.74

If you are using the Rule of thirds the Safety Margin is always 0.67

Gas for the Dive = Capacity x Safety Margin

Gas for the Dive = 2760 x 0.74 = 2042 ltr

Max Dive Time = Gas for Dive / (SAC x Depth Pressure)

Max Dive Time = 2042 ltr / (18 ltr/min x 3 bar) = 2042 / 54

Max Dive Time = 37.8 min

Obviously this s an average dive estimate so if you will be working harder than normal then account for this by increasing you SAC. In a stressful situation it is easy for a SAC rate to double if not triple!

If you use this set of rules then as far as a dive plan goes you should never run out of gas. During the dive is when gas management becomes key. You need to keep a regular check on you SPG throughout the dive and have a set turn pressure at which you will end your dive. Also you should be able to tell if you are using your gas more quickly than expected and shorten your dive accordingly. Trust me, no dive is ever that good that it is worth pushing past your planned end gas pressure. 

Safe Diving Practice and Problem Solving Part 1 – Know Your Limits

One of the most important skills a good diver needs is to be able to handle and solve any problem that arises underwater. This then allows then to make a controlled and safe ascent to the surface to dive another day. Most major problems arise due to a series of lesser problems, which after a point can really leave you in it. For example running out of air is caused by not checking gauges often enough, not having enough gas for the dive you have planned (depth or time), not properly maintaining kit (free flows) and being too far away from your buddy or not having a redundant air source. All of these are simply solved problems that can result in catastrophe.

The above diagram (the Pit of Despair) shows the chain of events that can lead to a lung overexpansion injury, one of the easiest diving injuries to avoid.

This part of problem solving is going to focus on knowing your own ‘Personal Limits’. All divers should be aware of how good a diver they are and the point at which they start to feel outside of their comfort zone. Don’t kid yourself; we all have limits and points at which we are no longer comfortable (these may also change from day to day, dive to dive). Know these limits and stay within them.

The easiest limit you can identify, and yet the one most often broken, is that of certification and depth. This limit is stated in black and white on your certification card and diver training. To an Open Water diver you might not see the difference in diving to 30m over diving to 18m or a deep diver the difference in diving to 50m over 40m and some of the time there might not be a noticeable difference.   However, you haven’t had the training to plan a dive beyond your qualification and how to deal with the situations when it goes wrong. Think back to your Open Water course, you spent most of the time learning what to do if it goes wrong:

• ·         You run out of Air
• ·         Your Mask floods or comes off
• ·         You lose your Regulator

Diving itself is pretty easy and very enjoyable when it is going right. You swim around, breath and look at some amazing sights, but when it goes wrong you need to know how to deal with it. Trust me a problem at 50m is much different to that at 40m and at 30m it is very different to that at 18m. So first of all to be a good and safe diver able to deal with problems know and stick to the limits of your certification and experience. Remember they are not targets to be met but limits to be adhered to, this means a newly qualified Open Water diver should build up to 18m and not make it your first unaccompanied dive after certification .The same goes for whatever level you might be. Think of the limit set on any certification you get as the limit for an experienced diver of that level. 

Scuba Spud Blog Introduction

Scuba Spud Introduction

I am a scuba diver who first took to the water in 2002. I became a diving professional in 2008 and have been teaching people to dive ever since. This blog is a gathering of my thoughts and feelings on scuba diving and also how I think that it should be approach at all levels. I do not profess myself to be a world expert and the views and opinions here are drawn from my experiences as both a recreational and technical diver. I have had the pleasure of diving with and learning from a large number of different instructors and training agencies throughout my diving career. In this blog you will also find points where I have drawn upon my experience as a Martial Arts Instructor and Mechanical Engineer as these all influence the diver that I am today.

I hope that you enjoy reading my work and I am always open to comments, discussion and input from people who are also interested in expanding their knowledge of the subject.

Good and Bad Buddies

Choosing a Buddy

There are many divers out there and many potential buddies. What you will find though is that all good buddies are divers but not all divers are good buddies. A good buddy is a very subjective view and depends mostly on the requirements of the person looking for a dive buddy. Coming from a family of divers I was always lucky enough to have a number of people to choose from and as we learnt in very similar ways we found ourselves as natural buddies for each other.

I think the main requirements for a diving buddy are:

• ·         Communication
• ·         Experience
• ·         Qualifications
• ·         Awareness of Personal Limits
• ·         Shared Goals and Interests

Communication

Communication is a very personal need and often changes as your experience and comfort levels change. As a newly qualified Open Water Diver the level of communication is required more often and in more detail of everything you are each doing. As you progress this communication between familiar buddies might become a knowing nod. The most important aspect of communication that both divers are aware of the type and level of communication that each of you need and that they are willing to accommodate their buddy even if the level of communication is more than they are normally used to.  The willingness of a diver to accommodate a fellow diver is often a positive sign of their ability as a buddy.

Experience and Qualifications

Qualifications aren’t everything and experience doesn’t mean a good buddy (or sometimes even a good diver). When it come to a buddy team it doesn’t matter if the divers are equally qualified or experienced as long as the dives they plan are to the level of the lowest qualification and least experienced member of the team. Within this no diver in the buddy team should feel pressured or forced to dive beyond, or even to the limit of, their experience. A good buddy and buddy team should encourage each diver to dive within their limits and to slowly grow their experience at a sensible rate.

Awareness of Personal Limits

Any good diver and good buddy should not only be aware of the limits of their buddies but more importantly their own personal limits. The only diver who can make you dive beyond your limits is yourself and no qualified diver should go on a “follow me” dive which they are unable to finish independently at any point. If either buddy were to dive beyond their limits then at that point they are not only putting themselves in trouble but also placing a burden on their buddy and putting them at risk as well.

Shared Goals and Personnel Interests

The most important aspect of any buddy team is a shared interest or goal. It is no fun diving in a team where you aren’t getting what you want out of your diving and after all we all dive for fun. A goal or interest can be anything for exploring wrecks, fish spotting or underwater photography. It is often possible to accommodate different dive interests within the same diving plans and so as long as everyone is happy then this is often the easiest aspect of a buddy team to meet. It is also the reason why many buddy teams eventually part ways as interests and goals change, especially if one of the divers wants to take their diving in a whole new direction which my require more equipment or training. So enjoy every buddy team you dive with while everyone is gaining from the group but don’t be afraid to find a new set of buddies to help you explore your next level of diving.

These are the aspect that I always consider when selecting a dive partner or when diving with someone new. As a dive instructor you don’t always get to choose your buddy but at least you can be aware of the type of diver and buddy they are. The other side of a buddy team is you as a diver and buddy. I always look at myself and my buddy and the type of team we make and what we each offer to the team.

  

                       

The triangle of diver experience is a simple tool to work out what you at least, if not others offer to any buddy team. No matter where you currently sit in the triangle it is not a problem as long as you are trying to move up the triangle and dive within your limits and the limits of the buddy team.  The strongest team is obviously 2 Self-Reliant Divers working towards a common goal but that doesn’t mean other teams cannot be successful if working well within their limits. Below are my description of each of the levels of divers, what they offer to the buddy team and how to achieve this level.

New Diver with Limited Experience

This can be an Open water or Advanced Open water Diver (or equivalent levels) who has a few dives under their belt and is still enjoying the wonders that scuba diving can offer. They can offer a new light on diving and an unbounded excitement for every new experience they have underwater. They should still be striving for a greater understanding of the subject from courses and more experienced divers around them.  In a buddy team they offer enthusiasm and excitement and a spare reg and a tank of air to their buddy when they needed it, more than this and they are often putting themselves in more danger than they realise but if they dive within their limits then this should not be a problem.

Diver familiar with Air Sharing Techniques

This is a diver with more experience in the water and their surroundings and has begun to develop a greater awareness of those around them. They may be an Advanced Open water diver or a newly qualified Rescue Diver. They are more comfortable with the techniques or air sharing and can help their buddy with basic problem solving.

Diver Able to Self-Rescue

A diver trained in basic rescue techniques with some reasonable diving experience will fit into this group of divers. They are able to deal with most problems for themselves before the cause any real issues and in the case of an emergency they can solve the problem themselves though it may need the interaction of another diver to supply air. They offer a good stand point as a buddy as their experience and skills means that you can real get on with enjoying the dive. Most rescue divers fit this group.

Experienced Diver able to Aid/Rescue another

This group of divers can make great buddies as their greater level of experience can be a great asset on any dive and when a problem arises they can resolve it before it escalates, either for themselves or others.  Most Divemasters and Instructors fit this group along with more experienced Rescue divers.

Self-Reliant Diver

A self-reliant diver is the pinnacle of being a dive buddy. They are a very experienced diver with the skills and equipment to complete any dive they do totally by themselves. This allows them to be an excellent buddy as they are able to fully aid another diver without issue to themself. A buddy team of multiple self-reliant divers can offer the perfect mix of diving experience. Very few divers, even instructors, meet this requirement. The investment in skills and equipment to reach this level can be extensive but well worth it. This should be the aim for all divers to achieve, however even if you fall into this group you don’t know everything and should not stop striving for improvement.