Deep Diving: An Introduction
Why Go Deep?
Diving manages to collect a massive variety of very different people together into one category: divers. Diving is a sport to some, to others it’s a hobby. I’ve met divers who are in it because it helps them keep fit and I have also met people who dive purely to escape their spouse’s nagging. Diving offers all this and much more to many people, but there is one thing that almost everyone takes from the pursuit – the peace.
I have never met a diver who dislikes the fact that the only things you can hear when diving is your breathing and your bubbles, for some it’s the reason they dive (I have a friend that dives in zero viz regularly purely so she can enjoy her bubbles). I have even heard diving compared to meditation in the way that it makes you focus on your breathing and your body. I feel the same way to an extent, I really enjoy the relaxation that comes over me from breathing slowly and deeply, doing an almost yoga-like swim and looking at relaxing images. I feel this most strongly when I go deep. The deeper I go the more intense the feeling of solitude and of contentment. This comes from a number of things but mostly I enjoy the sensation of getting narc’d (more on this later) and the fact that sound becomes more remote the further you descend, to the point where I feel almost disconnected from my body.
Ok, enough of the hippy crap, apart from feeling really chilled when I go deep what are the other reasons for going down where it’s grey? One reason I would consider trading a long dive for a deep one is so I could explore a well sunk wreck. It is common for wrecks to be scuppered in deeper sites to make them less dangerous for other vessels sailing over the top of them. In other cases the ships simply sank, they weren’t planned events so they sometimes ended up in inconvenient places. When a diver is really keen on his wrecks he will surmount almost any obstacle to get at his prize. These guys are often extreme tec divers solely so they can sit on the bridge of a big cruiser.
Search and Recovery
As with ships sinking in inconvenient places, we drop or loose other items overboard when we go diving, it’s a fact of life but no less frustrating! When this happens over a deep drop-off then it falls beyond the average diver’s ability or experience to retrieve it. This is where those deep freaks become really useful as they will almost certainly delight in grabbing a lift bag and plunging down after your camera, keys or weight belt! Search and recovery is also a code term for the looters of the sea. Often those divers who were madly excited about sitting on the captain’s chair will also ensure that they take a souvenir back to the surface with them. I won’t speculate on the morals of wreck robbery, but I will say that you’d best be careful if you want to indulge your mariner’s curiosity with a heavy memento as there have been some nasty accidents with bringing bulky objects back to the surface.
A less common reason for going deep is to go searching for different fish and life than is found at the surface. This is often a fairly fruitless endeavour because the light density at depths greater than thirty meters is not sufficient to support coral, which in turn makes the life at this depth very transitory and well spread out. It is possible to see some amazing creatures when your down deep (often large game fish will come down here for different reasons), but it’s in no way a certainty.
This is an even less common reason for deep diving, but for the adrenaline junky it is a fantastic one! There are a number of predominant prevailing ocean currents that have no effect on surface waters but are very strong on the bottom. Some of these currents are channeled along a wall or drop-off which makes for a spectacular dive. I would hasten to warn novice divers away from attempting this kind of dive unless you are accompanied by an experienced drift/deep diver because navigating at these depths is tough and ensuring you don’t get caught in a downwards or upwards current is imperative!
For the average deep dive (twenty-five meters to forty meters) the equipment list looks very similar to that of a shallow dive but there are few additions that usually don’t prove necessary but they can make the whole experience much more pleasant and possibly a little safer.
- Balanced Regulator – This isn’t really a specialist piece of gear these days as most mid-ranged and higher end regulators are balanced. The balancing refers to the way the first stage modulates the air pressure from high tank pressure to intermediate hose pressure. If you took an unbalanced regulator on a deep dive it would mean that as you descended it would feel harder to breathe from the second stage because the first stage wasn’t balancing the air pressure with the surrounding ambient pressure of the water.
- Flashlight – This might seem a little overkill to those divers who dive in clear tropical waters with nothing worse than ten meters of visibility, but even those divers might appreciate the extra light source when they get very deep. It is especially useful for examining fish or coral in detail as the colours will be very washed out at that depth (more on this later too!), and a flashlight is able to reintroduce the colour which can make an interesting fish look amazing.
- Safety Sausage (SMB) - I am a firm believer that all diver’s should carry a surface marker buoy on all dives. The safety sausage is a no-brainer, it makes perfect sense to carry something that packs up small that will make you much more visible on the surface, it will also make other boats aware of your presence below them which might help you avoid a short haircut from a propeller! It makes even more sense when you think how lost you can get when deep diving, so being able to signal the boat to come get you might be quite an attractive capability.
- Reel - The reel is a really versatile utility that is useful in a number of ways; you can use it to launch your safety sausage quickly, you can use it as a buddy line in bad viz, you can use it for wreck or cave penetration, you can use it to conduct a spiral search pattern and you can even use it to repair a piece of gear in a pinch.
- Adequate Exposure Protection – This is another one that is very regional specific, but in essence all I want you to remember is that in most places it gets colder as you descend, so maybe going in a little warmer than usual might help. It is also pertinent to consider how warm you’ll be when you are waiting for a decompression stop to tick over. Those stops can make you cold very quickly.
- Pony Bottle – This is not something that I use, but I’ve seen plenty of divers pull them out on the boat. They are very easy to use and they often simply attach to your main tank which makes them fairly convenient. The problem I have with them is that they really don’t hold much air, you might get as much as fifteen mins of breathing time on a big one but for most divers, it’s simply not likely that they will be caught out with no air and no buddy to aid them. It’s a technophile toy, but a bulky one that makes air travel costly.
- Dive Computer – Another item that I think no diver should enter the water without, but often diving is a spur-of-the-moment, holiday decision which leaves you without gear. For those divers I implore you to go beg, borrow or steal another computer for the dive because things like decompression stops, ascent rates and surface intervals are a nightmare/impossible to calculate on a standard RDP. Deep diving has too many variables to leave it to chance, just grab a computer and make your life much easier.
- Reference Line – This is a really good idea for the novice deep divers among us because if you have a line or can follow the bottom you are considerably more able to deal with equalisation problems, nitrogen narcosis and to perform adequate safety stops. Though I must confess that I much prefer descending to a deep dive in free fall because I find it really fun – it’s like base jumping in slow motion!
- Safety Stop Bottle and Weights – This is sometimes called a safety stop station and is usually hung at around five meters so that divers can rest there during their safety stop. It also means that if the diver gets to the station and finds they are very low on air, they can breath from the emergency tank while they perform the stop and then ascend on their own tank. Ensure that you turn the tank on before you sink it because otherwise water will flood the first stage and damage it. Sometimes the station will have spare loose weights which are there to compensate for the excess positive buoyancy that you’ll have at the end of the dive, though I think this is cheating – just weight yourself properly at the beginning of the dive!
- Emergency Oxygen – This should come as no surprise to any rescue divers out there. Emergency oxygen is the first treatment you should administer to any diver with suspected decompression sickness or a lung over-expansion injury. Make sure you are familiar with its operation and that you know where it is kept – don’t rely on others to know its operation, they may be the one’s who need assistance!
Diving has inherent risks, this isn’t news to anyone. The risks are usually blown out of proportion by those who are not familiar with the real science of diving. It is very unlikely for a diver to get hurt while enjoying their hobby, but there are certain things that I can say with something close to certainty will hurt you if you ignore the basic rules of diving – rapid uncontrolled ascents, breath holding as you go up, touching things you shouldn’t and ignoring the dive tables. These are all well known dive dangers that most divers are well aware of and are prepared to avoid (and thus makes their dives safer). Deep diving is not fundamentally different from “shallow” diving because all the same rules apply, only they now apply a little more severely.
Nitrogen Build Up
One of the main issues with deep diving is that you take on air at high partial pressures which means it’s like breathing anything from eighty percent nitrogen to hundreds of percent nitrogen on the surface. The partial pressure of oxygen is also higher, it goes from twenty-one percent up to over a hundred percent, and has the same effects as it would on the surface if you breathed one-hundred percent oxygen.
If a gas is highly pressurised in a fluid filled container (which our body acts like) then it will dissolve into the liquid at an amount which is directly proportional to the pressure of the gas. What this means is as we descend on a deep dive, the gas pressure increases which makes it more able to dissolve into our blood and tissues. This is perfectly safe and we are able to reverse the process by simply reducing the pressure (ascending). The problem arrises when we reduce the pressure too fast by going up quickly as it allows bubbles to form in the tissues (think of the way a bottle of coke is still until we release the pressure by opening the lid – this makes all the carbon dioxide form bubbles and escape). The key is to “open the lid” carefully and slowly which stops the gas from bubbling up i.e. ascend slowly.
Deep diving loads us up with a large quantity of nitrogen which means we have to go up even slower than on a shallow dive, sometimes you will have to stop for a while at certain points (denoted by your computer) to allow your body to catch up and dump the nitrogen smoothly. These are called decompression stops and if your computer says that you require one then it is imperative that you abide by it. These are not necessary in normal shallow dives, but if you exceed your no-decompression dive time then you will need to plan for decompression stops (ensure you are well insulated, have good buoyancy and have ample air).
There is also a massive rise in the amount of schools that offer blended gas mixes or “nitrox” which is simply a breathing gas with less nitrogen and more oxygen – this means the body will take on less nitrogen and this will make for a longer no decompression dive (or shorted decompression stop).
I said above that there was no issue with loading up on excessive nitrogen which is true to an extent in that there is no health hazard with the gas, though it does have a physiological effect. To put it simply, nitrogen in high partial pressures manages to disrupt and slow the neurones in your nervous system. This is not dangerous but it has some strange effects on your senses and mental capacity.
Many describe being “narc’d” as being a pleasant sensation of relaxation which has led to the name “the rapture of the deep” being bestowed upon this condition. Everyone feels different things when they get narc’d and everyone gets it at different depths and different severities. I am the only diver I know that gets my kind of narc; tingles on my skin, a pleasant sensation behind my eyes and a taste in my mouth that can only be described as a smooth creamy taste. I don’t tend to get much else in the way of symptoms, my head stays fairly clear until I get very deep. Some people really struggle with keeping their mind clear as narcosis also impairs your mental capacity (which can be a problem if you require a cool head to attend to an emergency). The effect has been described by the “martini law” which states that diving at thirty meters is the equivalent of drinking two martinis and that every ten meters afterwards is another martini. This is a tongue-in-cheek way of looking at the phenomenon but it helps to give you an idea of the effects you might experience. The law also applies in the same way that one person might have three alcoholic drinks and be able to function nearly normally, whereas another might be singing on top of the bar after two cocktails.
Narcosis is unpredictable which makes it dangerous, check your buddy and ascend a little if you think either of you are getting foolish. Some people have gotten so euphoric that they’ve removed their regulators from their mouths because they thought they could breathe under water. Keep a close eye on it.
There is almost certainly going to be a diver in your group with a small leak coming from a piece of his gear which, under normal circumstances, is no problem at all. However, we must remember that when we dive deep the gas that is vented into the water is much more dense than at the surface. This means that a leak that will cause a tank to loose two percent of its air in sixty minutes at ten meters will loose eight percent of its air at forty meters. This is not a huge amount of air, but it might be necessary gas for all the mandatory decompression stops that the computer will plan for you.
The simple way to solve this minor problem is by ensuring all your O-rings are in good order, performing a thorough buddy check at the surface and by performing a “bubble check” at a couple of meters as soon as you submerge. This involves each diver in the group slowly rotating full circle and the other divers watching to see if any small bubbles are escaping. If there are bubbles then at least you won’t be too far from the boat or shore to quickly jump out and install a new ring.
This is a triple tip (value for money!) because visibility is affected in three different ways when you go deep:
- First, natural light becomes increasingly less vibrant as you descend, this is because the water absorbs the light, so the more water – the less light there is. What this means is that when a diver goes very deep he will find the water becomes very dark and he will appreciate his flashlight, especially if he wants any chance of looking into a cove or hole.
- Secondly, this light absorbing phenomenon does another trick because it doesn’t just soak up the light equally, it works through the spectrum from the lowest frequency (red) through to the highest (blue). What this means is by the time the diver has reached twenty-thirty meters or so they will not be able to see the colour red by natural light, it will appear grey. This can be combated by flashing your torch on it because the torch light still has all its red in it’s beam.
- The Third way in which viz is affected when you’re deep diving is from the sediment that deep sites often have floating in the water which can lead to a very short sight range. This is not universally true, but it is often the case that the first fifteen meters of a dive site are clear and then you hit a soup layer than reduces your viz from twenty meters to two meters. This can hamper navigation somewhat and would be helped by a light to pierce the sediment (sometimes) and by relying on your compass.
Deep diving is a real pleasure that gives me a fantastic feeling of excitement before I go down and tangible feeling of relaxation as the sound of my bubbles dies away (the water pressure makes the sound echo much less, so sound becomes quieter and more remote which is very pleasant). It is also a key to many difficult to access dive sites and wrecks which makes it a valuable skill to learn. The important thing to remember is that deep diving is a skill, which means it takes practice and tutoring to dive deep safely. Pay extra attention to the basic rules and learn how to use your equipment intuitively so that the only thing you need to think about when you’re down there is the silence.
Do you enjoy deep diving? Why do you do it? Have you ever had any problems or pleasant surprises when you’ve went below thirty meters? What are your nitrogen narcosis symptoms? Please let us know in the comment section below!
Happy (quiet) bubbles!
By Jamie Campbell