Dive Theory
Improve your air consumption
Ever wondered why your buddy comes up with a 100 bar while you are down to 50 bar even though you tried so hard not to run low on air before him as it happened many times before?
"I will need the biggest tank that you have, I'm a heavy breather!" is a sentence that we hear all too frequently in our dive centres. While this is not a problem and we do have plenty of 12 L tanks most of these people entirely miss the point. It is usually not the tank that is too small, but rather the air consumption of the person using it is too high.
We have all asked ourselves at some point during our diving life how to get more out of our SCUBA tanks.
It is the question any Instructor gets asked on a daily basis and the crucial factor that limits us in how long we can stay immersed in this stunningly different world.
Let’s start by taking a close look at the factors that determine how much air you use:
Man or woman
Generally speaking if you happen to be a man you’re having a disadvantage already. Your body has a higher percentage of muscle mass compared to your female’s buddy, and muscles happen to need a lot of oxygen.
So, a small advantage from mother nature for all the ladies out there.
Physical Condition
Everyone knows that especially as a diver you should maintain good physical and psychological health.
So obviously being heavily overweight is affecting your air consumption in a negative way because your body finds it harder to supply all your tissues with Oxygen. On the other hand, if you’re a professional bike racer or swimmer you do have a much bigger lung volume than the average diver which in turn means you need more air to fill those big lungs all the way up.
As so often in life the golden middle is the right way to go!
Dive profile and conditions
The deeper you dive the more air you’ll use. This is due to the higher density that your air has at a greater depth.
As well swimming against even a slight current means your heart rate goes up as you do and your body again needs more oxygen to keep up with that.
Being aware of these factors is an important step in understanding how you reduce your air consumption.
Alright, we know why you are here so let's get one thing out first. There is no magic trick or secret formula we will tell you right here to become a turtle like diver. There are however a variety of small incremental steps one can take to slowly but gradually improve their air consumption.
Let’s have a look at 9 ways to reach this goal:
1. Breathe slowly and deeply
Breathe consciously as if you were doing yoga. Always fill your lungs all the way up and try to stretch the in-and-or exhaling process for as long as you can without it feeling uncomfortable or unnatural.
It helps to count the seconds while you exhale in your head: 1..2..3..4..5..6.. and then slowly inhale and fill your lungs all the way up. While you exhale your heart rate slows down and therefore your oxygen need as well.
You can already start on the boat while you do your Buddy Check and breathe consciously and slowly in and out.
Always remember the golden rule:
Don’t hold your breath! You might think you’ll use less air but the opposite happens and it is actually dangerous and can lead to serious lung overexpansion injuries
2. Stay physically fit
One approach would be to lower the creation of CO2. This can be achieved by mainly lowering our exertion levels underwater. When was the last time you worked out and went for a long run? By having a good basic fitness level you will automatically increase your body's tolerance levels to exercise. That small current on your next dive won't be noticeably to you when you are physically fit, but your beer drinking couch potato of a buddy will be out of breath soon.
3. Perfect your Buoyancy, Trim and streamlining
Constant struggle not to pop up or dragging over the bottom isn’t just bad for the environment and your body but also makes you use a lot of air. Are you still using your hands for moving around underwater, even though it's just a little bit sculling? You are using muscles unnecessarily, thus increasing your carbon dioxide levels.
Only if you have a good trim and streamlining (you are in a horizontal position and none of your gauges or equipment dangling) and know the right amount of weights you’ll be able to move around in an efficient and energy/air saving way.
4. Dive slowly
The slower you dive the longer your air will last you plus:
You are going to find much more cool stuff because you simply have more time to take your environment in.
The faster you move the more air you’ll need!
5. Stay shallow
At depth you’ll use more air. If there is no good reason to go deep don’t do it.
You are going to save air and have a more colourful dive in the shallows (red already disappears below 5m).
Plus, often the most beautiful coral is in the shallows anyway.
6. Propulsion technique and fins
A good propulsion technique goes a long way in increasing your air consumption as well. The flutter kick is one of the easiest methods to learn underwater, unfortunately it is not one of the most efficient kicking techniques. Unlike on land you can use your momentum to glide through the water instead of constantly kicking. A good technique for this is called the frog kick. Only occasionally kicking and gliding the rest of your dive will lower CO2 release greatly.
What helps with that, are a good pair of fins. If you want to find out more check our Blog about own fins
7. Go with the flow
If you can, go with the current and do a drift dive. It’ll save you loads of air.
If you can’t get around it use big and efficient but slow kicks and stay close to the bottom or topography to avoid breathing too fast or even overexerting yourself.
8. Watch for leaks
Even if it’s tiny, change it or get it fixed by a professional.
Divers often don’t realise that their equipment is leaking and it’s not only dangerous but can also cost you a considerable amount of air.
So, make sure your equipment is serviced regularly by someone qualified.
9. Dive as much as you can
If you only dive once every 3 years you probably won’t improve much.
Dive as often as you can and you’ll see that it’ll get easier and easier and one day you use just as little air as your Instructor or your female buddy.
We are happy to help you improve your air consumption, book your dives with us now!
How to calculate the right amount of weights
Are you one of the divers coming to dive centres and asking for 10 Kg to 14 Kg because you are a floaty person? Drop that number of weights down drastically, it adds unnecessary workload to your body. In this article we will explain how to determine the right amount of weights for you.
Imagine taking a six-pack of water and carrying that for 45 - 60 minutes from the supermarket to your flat. That is the equivalent of diving with 12 Kg when in reality you needed 6 Kg for the dive.
Ideally you have just enough air in your tank that at the end of your dive, when you hopefully have a bit more than 50 bar in your tank, that you are still neutrally buoyant.
First factor: The Tank
You will start your dive with a full tank of air. We will have to calculate how much weight it is going to lose when it is at around 50 bar. Let's assume we dive with a standard S80 aluminum Scuba Tank (80 cubic feet), the most commonly used diving tank. Let's convert these cubic feet to litres which will give us 2265 litres. We could bore you with the ideal gas law equations here or you could believe us that 1 liter of air weighs around 1.2 gram at sea level. If you were to breathe your tank from 200 bar down to 50 bar you will lose nearly exactly 2 Kg (2265 * 0.75 * 1.2). A standard Luxfer S80 tank is 1.6 Kg negatively buoyant when full, leaving you with only 400 grams of positive buoyancy towards the end of the dive.
Different aluminum tanks have different characteristics, but the most positive buoyant one that a normal diver will probably come across is a Luxfer 80 which gives 1.4 Kg positive buoyancy at 50 bar. The myth that aluminum cylinders are very positively buoyant is widespread, but completely unfounded. Catalinas C-Series tanks for example are all negatively buoyant, even when completely empty. Luxfers S-Series is ever so slightly positively buoyant when completely empty that it hardly makes a difference in weight calculations.
Other factors: equipment and body mass
A Large 5mm long wetsuit will give around 3 Kg of positive buoyancy. Taking fins, mask and your BCD most combinations will give you not even a total of 1 Kg of positive buoyancy, if at all.
Let's add up those numbers above. We realise that equipment towards the end of our dive adds a little over 5 Kg of positive buoyancy. Of the people that take 12 Kg on their dives who here really thinks that they can casually swim along in nothing but their swimwear with 7 Kg tied around the waist? The numbers above swiftly shift into the direction of taking less weights when we assume a smaller, shorter or thinner wetsuit or a steel tank. 5 Kg of positive buoyancy for equipment is fairly generous for diving in the tropics and depending on the equipment the real numbers will probably be closer to 2 or 4 Kg.
Body composition plays another role in how much weights you need. Everyone heard the phrase "fat floats" which is very much true.Although everybody is built different the standard human body density to water is 0,98 which means we very slightly float. In salt water very few people will need more than 1 Kg to sink.
Buoyancy check
We cannot stress enough how crucially important a proper buoyancy check before your first dive is. Take your time and find out how much weight you need. Jump into the water fully equipped and take just enough weight that you float at eye level while holding a normal breath. We repeat, a normal as in you being at rest, breath. The difference between a normal breath of 0.5 liter and a full breath can easily add up to more than 3 or 4 Kg. Once you added enough weight to float at eye level add an extra 2 Kg for the end of your dive when your tank gets towards your reserve. There are very few people that would genuinely need anything close to 10 Kg using the above calculations. Most end up with between 3 or 8 Kg.
Of course the above numbers are a generalization and we assumed diving in a tropic environment but the point we are trying to bring across is that most people tend to take more weights than they really need. We made this point to further reduce our effort underwater, resulting again in an improved air consumption.
Buoyancy control – be a better diver
We all want to be one of those divers who can hover perfectly still over the reef and glide effortlessly through the water. I remember, on one of my first dives, noticing my instructor’s perfect buoyancy and wanting to know his secret.
The PADI Peak Performance Buoyancy Specialty reveals all the tips and tricks to get your buoyancy under control. This is not just for newbie divers, anyone can benefit from fine-tuning their buoyancy.
By improving our dive skills, we use less energy and less air. We also get a closer look at beautiful macro life while preserving natural beauty. Lastly, we also just look cooler!
What will you learn?
This specialty course consists of two open water dives with an instructor. You will do exercises and learn skills underwater, and maybe some fun games.
The goal is to improve your fin kicks (do you know how to swim backwards?) and your trim, reduce the amount of weights you need and lower your air consumption.
Your PPB manual will explain all the theory behind it and also other useful information: How to calculate how much weight you need and how to streamline.
The better your buoyancy, the more fun you have on your dives. Book your PPB Specialty course and become the perfectly controlled diver you’ve wanted to be.
Can I dive with a medical condition?
As a dive centre, of course we would love to teach diving to every single person on this planet. Unfortunately, we can’t. Diving is fun and safe if you follow the rules and if your body is working properly. When underwater, we are under more pressure than usual. With a medical condition or medication, our lungs, heart and brain might not cope with that pressure.
Medical questionnaire
Before every dive course you will have to read the medical questionnaire. It contains questions about your physical and mental state. If you are healthy and are answering all questions with No, you are fit to dive.
If you answer one or more questions with Yes, you might not be able to dive.
Some conditions or medications will exclude you from diving immediately while others will still allow you to dive.
In some cases, we can consult our hyperbaric doctor, Dr Henrik Friis-Juhl and he will be able to help out.
Let’s take the question: “Have you ever had, or do you currently have back, arm or leg problems following surgery, injury or fracture?” If you broke your arm several years ago and you are now able to move it without pain and without taking medication, we will happily take you diving.
In other cases, you will have to consult a doctor that knows your medical history and the effects of your condition/medication while diving. This can be the case for asthma, diabetes, cancer and some mental disorders that are treated with medication.
Healthy does not mean fit to dive
If you have a medical condition and need to get a clearance from a doctor, make sure it clearly says “fit for scuba diving”. Not long ago we had a request from a guest who wanted to learn to dive. They had suffered from epilepsy in their youth so went to see the doctor that had treated them in that time. The doctor wrote a letter saying that they no longer suffer from epilepsy. It did not say they were fit to scuba dive. When checking with PADI if they would accept the letter as medical clearance, PADI said no. The guests had to visit a hyperbaric doctor who eventually decided that they were not fit to dive.
We know that these visits to specialists also come at a cost and hassle. However, if they clear you for diving, it will be the start of a wonderful diving adventure. If you don’t get a clearance with your medical condition then this is for good reason. You should be happy that you didn’t put yourself in a dangerous situation that could have cost your life. You can still enjoy the under waterworld, snorkelling is fun too!
What if I lie about my medical condition?
The easy way out to going diving with a medical condition would be to answer – dishonestly – all the questions with No. Well, this is not how it works. Not disclosing your medical conditions can put you at risk to injure yourself during a dive or even die. And it is not only yourself that you would put in jeopardy, but also your dive instructor.
We have an excellent team of dive instructors, but none of us are hyperbaric doctors. When in doubt, safety comes first and we will not take the risk of taking you diving. We would rather lose the business we would make with you than go to your funeral (not to mention all the paperwork that would be involved). This is not because we want to spoil your holiday but because we want to see you going home healthy.
In some countries like Australia, every diver who would like to participate in a dive course has to get a medical clearance from a doctor. One of the reasons of establishing this law was that too many divers died after lying on their medical questionnaire.
Come prepared
If you’re planning to dive with us and you have a medical condition, please download the medical questionnaire and let your physician fill in, sign and date the second page. Medical clearances are valid for one year.