Browsing Category Technical
The two diving skill sets every passionate diver should consider
This post about skill sets is for serious divers who are truly passionate about diving all that this world has to offer, every ocean, every lake, every river. If that’s not you, then read no further!
The world is your oyster!
To me, any body of water is diveable given the right skills and logistics, it’s just a matter of whether it’s worth your time or curiosity.
My endless curiosity has always made me wonder what’s just a little deeper, just around the corner, underneath the surface.
Over time, I’ve built up a set of skills that I think truly allows me to look at any body of water on earth and think seriously about diving it.
All the time in the world
The first limitation in diving is one of time.
No decompression time limits and gas volumes limit most divers to about an hour on each recreational dive.
However, with technical diving, these limitations are made irrelevant with the appropriate logistics and skills.
In a technical diving course, you’ll learn how to manage different gas mixes, allowing for deeper dives and extensions of bottom time.
You would also learn how to calculate the decompression time and gas necessary to accomplish this.
Once you have the ability to dive with multiple tanks, then gas volumes also become irrelevant.
It just comes down to how many tanks you can carry or stage during your dive. It becomes a question of logistics.
Technical diving isn’t only about depth, but rather about decompression.
This can be calculated for a 2-hour dive at 25m, or a 1-hour dive at 75m.
Either way, doing a technical diving course allows you to go past recreational depths and time limits, whilst ensuring that you have the knowledge to plan enough bottom gas and deco gas to complete the dive.
It’s only cold in space
After getting technical diving skills, the next limitation most people face is the temperature.
Extended duration dives tend to suck the warmth from you, even in 28C water.
Warm water diving is actually limited to only a few degrees of latitude north and south of the Equator, and only tens of meters below the surface.
Once past the Tropic of Cancer and Capricorn, and you’re definitely in cold water country.
This leaves large areas of water that you’ll definitely need a drysuit to dive in.
Why limit yourself to Earth’s wonders that are only in warmer locales?
What about diving between continental plates in Iceland, or the wrecks of the North Sea?
So, the next most important skill set is learning how to dive with a drysuit.
This does take some time to get used to, as managing thick undergarments is no walk in the park.
But once you do, then all the wonders of the northern and southern latitudes will open themselves up to you, as well as longer dives in warmer waters.
Get wet anywhere!
With these two skillsets, I truly believe it enables divers to dive anywhere in the world you might want to.
Overcoming depth, time and temperature limits are not easy and will take some time to accomplish.
But just imagine knowing you can dive anywhere in the world. What a rush!
Bonus skill – getting in over your head
As a bonus, here’s the third set of skills that I think a true explorer should learn – cave diving, the last frontier.
I personally learned cave diving not because of the caves, but rather for the skills and knowledge of how to do dives in overhead environments.
These skills come in very handy when diving in wrecks, sea caves, or any kind of environment where you don’t have a direct ascent to the surface.
The true skill here is in learning how to better plan and manage your gas supply to guarantee that you and your teammates can safely ascend to the surface.
Another important skill set that cave diving teaches you is line management.
This is very useful in any survey or mapping exercise and keeps you on your toes as far as navigation is concerned.
Now, get out there and dive!
And there you have it, my three picks for the skill sets that you should consider to be a limitless diver!
Should I use a 5 foot or 7 foot long hose?
There are two schools of thought regarding the length of a long hose.
5 or 7 feet (1.5 m or 2 m)?
Let’s explore where they came from and the rationale behind each of them.
7 feet – longer than the average human
The 7-foot hose came from the cave diving environment.
Divers would need to share gas, but sometimes having to go through a restriction swimming in single file.
This made the regular short hose unusable, as you wouldn’t be able to share gas with someone in front or behind you.
The 7-foot hose was used to that divers could have the out of gas diver in front of the donor in single file and still have enough hose to be comfortable (unless you were sharing gas with an 8-foot tall giant…).
Ocean divers then discovered that a longer hose would help in keeping the divers further apart, allowing for better maneuverability and comfort.
However, some people thought that the 7-foot hose was too long because you would never really be sharing in single file in an open water environment.
A 5-foot hose was then adopted as a compromise to having a longer hose to manage while sharing.
5 feet – still a long hose but is it too short?
Personally, I would always use a 7-foot hose, but not for the reasons of sharing ironically.
The longer hose is definitely harder to manage when you’re learning it, but overall, I think it loops better and stows away better into the waist belt or behind a canister light.
This holds the hose in position during the dive, and if managed properly, the hose will stay in that location and not move around.
The 5-foot hose would be trapped under the right armpit when used by a larger diver.
In some cases (8-foot giants especially), this can get uncomfortable to the point of not having enough hose length to turn your head to look left.
Smaller sized divers would not have this problem.
However, as the hose is not secured, it will float and move around behind the arm and potentially above the head.
This may create problems when diving doubles, as the hose extending from the second stage tends to get looped around the isolator manifold or right regulator and knob.
Once there, a sharp turn to the left can actually pull the second stage out of the mouth!
7 feet – a Goldilocks length
For these reasons, I personally would always recommend using a 7-foot hose.
It’s long enough for everyone to be able to tuck it securely under the canister light, or into the waistband.
If your waistband is tight enough, then the hose should not pop out on its own accord and float around.
Having stuff in places where they are secure is a big thing for me, as is keeping things nice and neat.
I really hate it when equipment comes loose and causes problems during a dive.
Equipment should be there to support me, not cause additional issues!
Are diving doubles and sidemount the same thing?
In terms of the number of tanks you might carry, sure, doubles and sidemount appear similar.
However, sidemount and backmount doubles differ in one crucial area – the isolator manifold!
Why would you ever need more than one tank?
Now, let’s start from first principles.
What are the reasons for carrying more than one tank in the first place?
Some might argue that gas volume is the primary reason, however, redundancy is a more important and valid reason.
On a normal single tank (especially one with yoke valves), O-ring failures (tank neck, tank knob and yoke valve) are relatively common.
The next most common thing to fail in scuba gear would be the regulator setup, as there many O-rings and hoses that can rupture and cause a catastrophic gas loss.
Single points of failure are dangerous when diving
With single tanks, a gas loss from an o-ring failure in the yoke valve or the regulator will result in an immediate out of gas situation.
In order to deal with this situation in deeper or more extreme dives where a direct ascent to the surface is impossible (a decompression obligation or an overhead environment), we would require a secondary gas supply so that we don’t go into an out-of-gas situation on a single failure.
Double your tanks, double your hoses, double your failures
A quick solution to this was to just carry another tank.
In the early days, people would just carry 2 tanks, with a full set of regulators on each, in essence, doubling up on the gas supply, but also doubling up on the failure points in the system.
However, what if halfway through the dive, you had one full tank and one nearly empty tank and a failure happened on the full tank?
This would leave you with a nearly empty tank, with no backup.
Clearly, this wasn’t an ideal solution.
What about connecting these tanks?
The best solution to this was connecting the tanks with an isolator manifold.
Two 300 bar scuba cylinders connected by an isolating manifold
Using this setup, we could have a single regulator failure but still have access to all of our gas supply.
The isolator is an important part of this setup because it would allow a diver to isolate an unfixable leak to just one tank.
This prevents an immediate out-of-gas situation because you would still have one regulator working.
Some might argue that the manifold itself presents a failure point, but in all my years of diving doubles, I’ve not seen a bad manifold failure happen in the water.
In most cases, if the manifold were to fail, it would fail during the filling or setup process.
So what about sidemount?
So where does this leave us in the discussion on sidemount vs backmount?
Sidemount was created because of a specific need to access ever smaller and tighter holes in cave exploration. Places where backmounted tanks would have limited access.
Diving sidemount in open water negates the benefits of carrying 2 tanks by reverting to the original idea of the independent doubles. This of course comes with the associated negatives mentioned above.
There are some benefits to diving sidemount that proponents argue on; that it’s easier to put on; easier logistically; better for the back, etc.
See my other article about diving sidemount in open water to get an idea of why I think that’s not so relevant.
However, when we come back to the main reasons of why we have multiple tanks, sidemount just doesn’t match backmount when it comes to redundancy.
What tools do I need for a dive trip?
It’s always good to have a small set of tools when you dive. Better yet, have them on hand in the boat! You never know when you might need to repair something just before a dive.
Here are items that are useful to have, but of course, not all are always necessary. I’ve listed them in terms of two levels of preparedness: An essential set of tools, and a hardcore-fix-almost-anything set of tools that would serve you well if you wanted to dive at the end of the world with zero logistical support.
The Essential 14
- Adjustable spanner, one small and one medium sized – For regulator hoses and SPG removal
- Screwdriver, one Philips screw head and one flat-blade – For canister lights, hose clamps, etc.
- Cable tie, 5 to 10 pieces – For miscellaneous attachments.
- Nylon line, 1 to 2m long – For tying bolt snaps and other miscellaneous attachments.
- Lighter – For burning ends of nylon line.
- Bungee, 1 to 2m long – For replacing necklaces and other attachments.
- Scissors or cutter – For miscellaneous cutting.
- Duct tape, 1 roll – Never leave home without this! Duct tape is useful for Nitrox labelling, holding stuff in place, and other general uses.
- Allen key set containing multiple sizes of keys – For port plugs on first stages.
- Scuba Multi-tool – Some multi-function scuba tools combine a few of these tools in one small, compact package, and these normally come with screwdriver heads, various Hex key sizes, and an O-ring pick.
- O-ring pick – For removing O-rings. (Note: A small one should be sufficient.)
- Spare O-rings – For port plugs, regulator hoses, and SPG spindles.
- Grease – For lubricating parts like the O-rings (Tip: Instead of bringing out a large tube of grease, a simple solution would be squeezing some grease into a small ziptop bag. It’s also convenient to use – just pop the O-ring in the bag, seal and slide it around with your fingers. Voila, the O-ring is greased!)
- Spare mouthpiece – In case you get so excited that you accidentally bite through the mouthpiece on your regulator.
And here comes the list for total preparedness at extreme dive locations where you’d want to have everything on hand, except the kitchen sink!
Fix-it-all
- Tank knob tool – Larger dive operations like dive shops and liveaboard boats should have this tool, but it’s good to have your own as you never know when or where you’ll be when a tank knob gets stuck!
- DIN or Yoke adapter – For times when the boat operator doesn’t have the type of tank valves that you need for your first stage.
- Spare inflator assembly – Good to have replacements on hand as inflators are fickle; the button spring is a salt sink that get sticky from just missing a single wash.
- Spare double enders and bolt snaps – Infinitely useful, these little things make carrying equipment underwater very manageable.
- Small metal parts like washers, wing nuts, LP and HP port plugs – These are useful if something breaks and you need to plug a first stage. Small washers and spare wing nuts for your backplate system are also useful. Place these in a small ziptop bag to keep them safe and secure.
- Seasick pills and Charcoal tablets – These are typically classified under medication, but these meds are needed so often, there’s no harm stashing them in your tool kit AND first aid kit.
Storage
Keep these tools in a small-sized waterproof box that you can stow in your dry bag. Avoid leaving them around, especially wet surfaces, as tools tend to get rusty real quick around seawater! To absorb moisture trapped within the box, place a small silica gel bag or unused cat litter (inside a tiny sock) inside.
Why use double tanks?
When asked this question, most people would answer that we use double tanks to get more gas for our dive. This is a valid answer, of course, but I think the more important reason is redundancy.
Redundancy: The inclusion of extra components which are not strictly necessary to functioning, in case of failure in other components (OED)
Running low on gas during a dive can be frustrating – we all know what it feels like to want to stay down longer and enjoy ourselves! The next logical step to overcome this limitation is to carry more gas, especially on deeper dives where a diver’s gas consumption will be much higher.
Without going into a discussion on decompression here, increasing gas capacity can be done in different ways, by carrying a larger tank, using a steel tank so you can fill it to a higher pressure, or carrying multiple tanks.
If one chooses the last option of carrying multiple tanks, one could consider simply strapping two single tanks together (called a sidemount or independent doubles configuration) to effectively double the available gas. So why not just do that? Consider a situation when a failure happens (for example, a faulty o-ring on a regulator or tank valve). The result is you lose the ability to access an entire tank of gas.
Another problem with the sidemount or independent doubles configuration is that you’ll have to double up on regulator hoses. You’ll need a primary and secondary second stage, an inflator hose and an SPG on each of the first stages. This in turn doubles the number of possible failure points. Not ideal.
That aside, we also have the issue of deciding which tank to breathe on. If we breathe on one tank fully, then what happens if failure occurs on the full tank that you were planning to switch to? (Sidemount divers will argue that there are ways to prevent this from happening, such as switching tanks at defined intervals to balance the gas consumption between both tanks, but these measures could lead to additional complications, IMHO.)
We can mitigate against some failures by using DIN instead of Yoke valves on our tanks, and by minimizing the number of hoses that we need, but the best method I’ve found is to dive with a double tank configuration with an isolator manifold.
So how is redundancy built into this configuration?
One important feature is the isolator manifold. In this configuration, we have two first stages, each connected to a tank valve, which are in turn connected to each other via the isolator manifold.
Two 300 bar scuba cylinders connected by an isolating manifold
With this set-up, a single failure on a regulator will not result in an immediate loss of half your gas. We could shut off the valve that the failed regulator is connected to, and effectively shut down the leak. Because of the manifold, we can still access all of the gas in that tank. In this situation, one failure will result only in the loss of some functions (one second stage and either the inflator hose or the SPG), but not in any loss of gas.
But what if the manifold itself fails, you ask? Well, this is where the isolator comes in. If any side of the manifold, or tank valve fails, then we could isolate the two tanks by closing the isolator valve. This cuts off the flow of gas from one side to the other, resulting in only one of the tanks draining, as opposed to both, if the valve was left open, or if there was no isolator.
When doing more extreme dives, whether you’re going deeper or diving in an overhead environment, you’ll want the confidence of knowing that failures won’t result in you losing so much gas that you won’t be able to get to surface safely. Personally, I’d say that’s a pretty good reason to have the heavy weight of a set of double tanks on your back!
To tech or not to tech?
This is a great question, as one of the first things people consider after they’ve completed their Advanced course is where to go and what to learn next. There are a few common paths, most notably the Rescue/DM/Instructor path offered by all the recreational agencies. The other path available would be tech or cave diving, a gateway to exploration and more “exciting” dives. Meanwhile, there are others who have no desire to do more, and are happy just traveling and clocking up more leisure dives.
All paths are great, and part of the beauty of diving is that it’s such a wide field that there’s something for everyone to feel passionate about.
Most people end up taking the Rescue/DM path, as it’s the more commonly available path, and some would argue, the cheaper option. Technical diving is less common and harder to get training for, but I’d argue that it is an equally vital part of continuing dive education. Divers should consider an “and” approach, rather than an “or” approach when choosing between the various paths.
Some people get into tech diving because they want to go deep, see big wrecks, or just feel the thrill of it. My personal reason was wrecks – the bigger and more interesting the wreck was, the deeper the water would be (typically).
I’d argue though, that going tech shouldn’t just be about going deep, which is the misconception that many people have. I’d argue that technical diving is about understanding diving a whole lot better. That, plus acquiring more skills, and removing some limitations of time, gas and decompression from any dive that you might want to do.
One important reason for going tech is the skills that you’ll gain. With more task loading (from carrying multiple tanks, for example) and the greater necessity for excellent buoyancy (because of high PO2 concentrations in deco gases – more on that in another article), you’ll need excellent in-water skills to become a technical diver. These skills aren’t just important because you’re a tech diver though; good buoyancy, good technique and good awareness are important on any dive. Just because you’re on a warm water recreational open water dive doesn’t mean that you should dive without good technique.
The knowledge learnt in a technical course also includes a comprehensive study of decompression, which is a factor in any dive that you do – and not just in deeper dives. Isn’t it prudent to better understand where the boundaries are, how better to manage your decompression, and what to do if you exceed the currently accepted no-decompression limits?
Another great reason for doing a technical course is to gain access to more gas, and to acquire the ability to choose the most appropriate gas mixture for the depth that you are planning to dive. What if you wanted to explore a large wreck or reef that sits between 25 to 30m deep? Or want to wait at a deep cleaning station longer to get a good video of the elusive thresher shark?
Dives like these, despite being within recreational limits, would be better served with a set of double tanks and EAN32%, extending the limitation of gas consumption and decompression, allowing you peace of mind to accomplish your goal! Better still if you carried a decompression tank as well, that would definitely allow you to do a two hour long dive!
Once you understand decompression procedures, are able to manipulate stage bottles and plan your deco gases effectively, this will remove any limitation on the type of dives that you might want to do.
This could mean spending more time on your favourite dive site, since you don’t have gas consumption or decompression limitations anymore. To me, tech means getting to do any kind of dive you might want to do, be it long and shallow or deep and short.
Everybody loves spending more time in the water, and this traditionally meant doing more dives. Wouldn’t it be more comfortable being relaxed underwater, enjoying and taking in everything at your own leisure, without worrying about decompression limits, or running out of gas?