4 Top SCUBA Diving Myths

OLYMPUS DIGITAL CAMERASCUBA diving has become a very popular sport. Everywhere there is a body of water (sea, ocean, lake) you will find most often than not a diving agency or club willing to teach you how to explore the marvels the underwater world has to offer.

However, there are still some common myths and misconceptions around that confuse and sometimes discourage non-divers to even try diving for the first time.

So, my fellow future divers (I have faith in you!) here are the 4 most common myths I have encountered during my diving days and the reality about them:

Myth #1. Divers carry a tank full of oxygen to breathe underwater

Surprisingly no. It is true that divers carry a tank (sometimes more than one, but we will discuss that on a different post). The tank is full of widely available, common air. Yes, the tank or cylinder (if you want to sound smart) is full of exactly the same stuff you are breathing while reading this.

For the brainiacs in the audience, air has only 21% of oxygen, the rest is a combination of other gases (mostly Nitrogen 78%) including argon and carbon dioxide.

The only difference is that the air in the tank is very dry. This is necessary to prevent rusting (humidity and metal don’t get along very well) and extend the tank lifetime.

There are special cases (technical diving, enriched air, etc.) when the tank might be filled with something different but the large majority of dives in the recreational world are done with common air.

Myth #2. Diving is all about how deep you can go

One of the most frequently asked questions I get when talking to non-divers is how deep can you go. When I tell them that my average depth is around 28 meters (92 feet) I can see the disappointment in their faces.

Depth is one of the elements about diving but not the only one. Diving is about the challenge of safely visiting an environment where humans are not commonly welcome (unless you can naturally breathe underwater, and if you can, please contact me immediately).

It is also about exploring the underwater world, full of life and colours that cannot be found elsewhere. It is about the excitement of visiting a sunken ship and imagining what life was onboard while exploring the scattered remains of the ship now home to countless different species of fish and coral.

The depth and the resulting increased pressure is something that divers spend a great deal of time understanding during training. In the end, all divers learn how depth and pressure work, but most importantly learn to respect them.
Different levels of diving certification will give you access to better dive planning and greater depths. But for recreational purposes, the depth limit is set at 40 meters (130 feet). Anyone that tells you stories about going deeper than that without the proper training/equipment is either lying or taking unnecessary risks.

The good news is that most of the life, action, and excitement can be enjoyed in the 10-25 meters (33-82 feet) depth range. So, as you can see, is not only about how deep you go but also about the entire adventure of discovering what the underwater world has to offer.

Myth #3. Shark Attacks

Thank you Hollywood and news outlets! Sadly when a shark attack occurs, the media immediately jumps and describes every gruesome detail of the incident and give the audience the impression that this kind of events is a common occurrence.

Nothing farther from the truth. Sharks are majestic creatures that will happily share their environment with the occasional visitor.

To put some perspective, consider that there are around 6 million active divers worldwide1 and according to the international shark attack file, between 1958 and 2016 there have been 2,785 unprovoked shark attacks, of which 439 were fatal2.

Simple math tells that: 0.0004% of active divers were attacked during a period of 58 years! Out of these incidents, 0.00007% were fatal. This is something the news outlets do not share when broadcasting a shark attack report.

To put even more perspective, according to the “list of 18 things more likely to kill you than sharks”3 available on the same report, it is far more probable to die of sun exposure, lighting or fireworks than a shark attack.

So, no, a shark attack is not something you should worry about while exploring the underwater realm. If you ever see one don’t panic, show respect and take a great picture! It will definitely grant you bragging rights.

Myth #4. Diving is a sport for guys only

No! No! and No! There is nothing that suggests that diving is a guys only club. On the contrary, most diving apparel companies produce equipment and apparel that caters for the girls’ needs and tastes.

There is also a growing number of female diving personalities and ambassadors that prove that diving is an all-inclusive sport.

The only requirement to get into diving is to get a proper training and certification from a reputable agency. There is absolutely no difference between males or females when it comes to the requirements and qualifications to get certified.

So, please if you want to dive, just go and do it! You will find that there are training alternatives available that will allow you to “discover” the experience before you commit to getting a full certification.

So, I hope that this clarifies a little bit more the wonderful world of underwater exploration and wish to see you soon making bubbles and enjoying the under the sea view.

-Stein

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Getting Your Weight Belt Right… With Science!

The weight problem

The human body is naturally buoyant (it floats). For this reason, a scuba diver must add weight (usually in the form of a weight belt with lead blocks) to ensure he or she will be able to descend and ascend in a controlled manner.

Due to the multiple factors that influence the calculation of the required weight for a belt such as water type (fresh vs. salt), diver weight, body fat, gear, temperature, etc. setting it up a with the right amount of lead can be a daunting task. Especially for novice divers that are still learning the ropes of buoyancy control.

This, more often than not, leads to an “improper” weighted diver who is either too heavy or too light and struggles to maintain neutral buoyancy. As a result, the diver uses more air than necessary reducing the bottom time and increasing risk.

Many diving agencies have developed “rule of thumb” guidelines to calculate the required weight but these usually don’t take into consideration all the factors that affect buoyancy and the approximated suggestions need to be adjusted continuously.

To prevent this and help fellow divers, this paper describes the physics of buoyancy with the objective to describe a more accurate method to calculate the weight requirements for any diver and condition.

So, buckle your belt up (no pun intended) take your calculator out and get ready to uncover the actual weight you need to put on your weight belt for your next dive!

Understanding buoyancy

When a body is placed in a fluid, two main interacting forces determine if it will float, sink or remain suspended: The buoyancy force (Fb) and the force of gravity (Fg).

To determine the body behavior in the fluid consider the following table:

Fb > Fg

Floats – Positive buoyancy

Fb < Fg

Sinks – Negative buoyancy

Fb = Fg

Neutral – Neutral buoyancy

Determining the buoyancy force (Fb)

Buoyancy force is determined by three factors:

  • The submerged volume of the body (Vs)
  • The density of the fluid (D)
  • The force of gravity (g constant with a value of 9.81 Newtons/Kg)

Buoyancy force is calculated with:

F_b =D\times V_s\times g

Calculating fluid density (D)

Diving only happens in water! This makes the fluid density calculation a bit simpler, however, there are a couple of things that must be considered: Water temperature and salinity. To determine the density, use the following table(1):

Temperature (Celsius)

Fresh water \frac{kg}{mt^3}

Salt water \frac{kg}{mt^3}

4

1000

1024

5

1000

1024

10

999.98

1024.94

15

999.2

1024.15

20

998.3

1024.22

25

997.1

1022

30

995.7

1020.56

Calculating the volume (Vs)

For diving, this is the most complicated element to calculate. Several factors must be considered to accurately determine the submerged volume. To simplify the calculation, only the most relevant variables will be taken into account:

  • Body weight
  • Body composition: since fat floats and muscle tends to sink, this must be considered on an individual basis
  • Tank weight and volume

Body volume: to calculate the diver’s body volume, it is necessary to determine the amount of fat and muscle. I suggest that a simplified version of this calculation can be done by using the body mass index (BMI) as a guideline. To calculate BMI(2):

BMI=\frac{(\frac {weight (kg)}{height (mt)})}{height(mt)}

BMI can be related to the percentage of body fat and body density according to the following table(3):

Category

BMI

Body Density

Fitness

<18.5

1.282

Normal

18.5 – 24.9

1.01

Overweight

>25.0

0.808

With these elements, diver body volume (Vd) is calculated with body weight (Wd) and body density (Dd) with the following formula:

V_d=\frac{(\frac{W_d\times 1000}{D_d})}{1\times 10^6}

Note that the operations with the constants (1000 and 1×106) are used to maintain the unit of measure integrity. The final result is expressed in m3.

Tank volume: For an accurate volume (Va) calculation it is necessary to take into account pressure after compression (Pc – typically 210 bar), Volume of gas after compression (Vc – typically 11 lts) and atmospheric pressure (Pa – constant 1.01 bar). This is expressed in m3 and determined by:

V_a=\frac{P_c\times V_c}{P_a}\times 1.225\times 10^{-3}

Total volume: Once these elements have been calculated, the diver total submerged volume is obtained as follows:

V_s = V_d + V_a

Determining the force of gravity (Fg)

Gravity is calculated considering: The total weight (W) and the force of gravity (g)

F_g = W\times g

Calculating total weight (W): To calculate the total weight consider the two main elements: diver weight (Wd) and tank weight (Wt).

W = W_d + W_t

Tank weight (Wt) varies depending on the material (steel or aluminum), volume and ambient temperature. To determine the total tank weight use:

W_t = W_e + (V_a \times d)

 To determine the tank weight (We) refer to the following table(4):

Tank

Weight (Empty) kg

Aluminum 11 lts (AL80)

14.2

Aluminum 13 lts (AL100)

18.5

Steel 11 lts (Steel 80)

12.7

Steel 15 lts (Steel 108)

20.8

The weight of the tank gas will vary depending on volume and temperature. To determine the density (d), refer to the following table(5):

Temperature (Celsius)

Density (kg/m3)

5

1.269

10

1.247

15

1.225

20

1.204

25

1.184

30

1.165

Calculating the required weight

Once the buoyancy and gravity forces have been calculated. the required weight (in kg) for the belt can be calculated with:

B_w = \frac {F_b - F_g}{D \times g}

Compensating for exposure suit and other gear

Divers wear a variety of exposure suits to adapt to different conditions such as water temperature, potential hazards, etc. To calculate the required weight to compensate (Wc) for exposure suit buoyancy consider the following table:

Add per mm (fresh water)

Add per mm (salt water)

Exposure suit

Kg

Lbs

Kg

Lbs

Full body 1 piece

0.884

1.95

0.907

2.0

Shorty (no sleeves)

0.442

0.975

0.435

1

If the diver is wearing extra gear, add the required weight to compensate according to this table:

Fresh Water

Salt Water

Additional gear

Kg

Lbs

Kg

Lbs

Hood and gloves

0.435

0.96

0.453

1

Calculate the total weight

The total weight belt (Wt) will be determined by Bw plus the required compensation for exposure suit and other gear (Wc). Additionally, due to the weight blocks availability at most diving shops, this number needs to be rounded.

As a safety measure and personal preference, a margin of +/- 10% can be factored into the final calculation to get the recommended weight belt range:

W_t = round(B_w+W_c)

Recommended weight range = Wt +/- 10%

Putting it together, a practical example

The best way to understand these calculations is with real life example:

A diver needs to calculate the weight for the belt:

  • Diver weight: 86 kg
  • Diver height: 1.70
  • Water: Salt @ 20 Celsius
  • Tank: Steel 11 lts @ 210 bar
  • Exposure suit: full body 5 mm
  • No hood

Calculate Buoyancy force (Fb):

F_b =D\times V_s\times g

Density (D) = 1024.22 \frac{kg}{mt^3}

Volume (Vs):

BMI=\frac{(\frac {86kg}{1.70mt})}{1.70mt}=29.7, then Dd=0.808

V_d=\frac{(\frac{86kg\times 1000}{0.808})}{1\times 10^6}=0.106mt^3

V_a=\frac{210\times 11}{1.01}\times 1.225\times 10^{-3}=2.801mt^3

V_s = 0.106mt^3 + 2.801mt^3=2.907mt^3

F_b =1024.22\times 2.907\times 9.81=29\times 10^3 Newtows

Calculate force of gravity (Fg):

F_g = W\times g

W_t = 12.7 + (2.801 \times 1.204) = 16.07 kg

W = 86 kg + 16.07 kg = 102.07 kg

F_g = 102.07\times 9.81 = 1.0\times 10^3 Newtons

Calculate the required weight (Wt):

W_t = round(B_w+W_c)

B_w = \frac {29\times 10^3 - 1\times 10^3}{1024.22\times 9.81} = 2.78kg

compensate for exposure suit:

W_c = 5 \times 0.907 = 4.53 kg

W_t = round(2.78 + 4.53) = 7 kg

Recommended belt weight range: 6 kg – 8 kg

Final notes and recommendation

Please note that to give credit to the sources that were used during the preparation of this paper, links have been added where you can click for further reference.

Remember that it is recommended that a buoyancy check is performed every time you change the diving environment, gear or conditions. Ensuring that you are properly weighted will make the experience safer and more enjoyable.

Feel free to distribute or copy this material as long as you provide a reference to the source.

Obviously, the author can not take any responsibility on how a diver applies this information.

Happy diving!

-Stein

Dive Log

2016-03-04 16.11.24

I love diving! Some of the fondest memories of my adult life are from  moments in or around water.

Since my diving adventure began, I’ve been a total of 59 hours and 38 minutes underwater breeding compressed air from a bottle strapped to my back and did it in 10 different countries.

Also, out of all the dives, 18% were ship wreck exploring expeditions, 48% reef reconnaissance missions and 34% were either, training, archeology or cenote dives.

How do I know, because I keep a dive log!

The funny thing is that most divers see the log keeping activity as a burden. But in reality it is  part of the adventure! A well maintained diving log is not only about numbers, it is a memories scrapbook that narrates the story of fantastic dive buddies (Vlad, Denise, Romina, Tino and Assaf I am looking at you!) and great underwater species sightings (eels, turtles, dolphins, even the ocasional shark!).

It is also a storyteller about how one becomes a better diver. My log shows all the things done right during the dives but also recounts mistakes to be reviewed and corrected in future dives.

So, as you write your own diving adventure (you have not started yet? what are you waiting for?) make sure you keep an accurate and detailed diving log. Use the format or media that best suits you. In my case, I keep both paper (otherwise how will I brag about all the cool stamps from diving shops I’ve collected?) and electronic (www.diveboard.com is my choice because is cool and free) versions.

And be sure to share your log!!! after all, we all like to brag a little bit about our diving feats. Don’t we?

-Stein

 

Why I love diving

The author diving in BaliI admit it, I love diving gear! I like the smell of neoprene and yes, I have a collection of cool diving accessories that I am not even sure I will ever use. I am a man! And we men have a genetically coded attraction to cool gear.

One of the attractive features of diving (certainly not the only one) is that it is a “gear intensive” sport. After all, the difference with many other sports when it comes to equipment is that diving gear is not only is super cool, but it is also a life supporting system.

Then, there is the challenge. Water is an unwelcoming environment for humans, an before you can explore its marvels you have to prove yourself worthy of it. You have to get certified, then learn the ropes by adding experience and more training one step at the time.

You have to always be attentive and humble enough to learn from every experience, to ask questions and let more experienced divers show you the road to a safer and more satisfying diving adventure. And for Pete’s sake, keep and updated diving log! It will prove and invaluable source of wisdom and good memories as you progress in your diving journey.

Discovering new places is also part of the adventure. More often than not, diving will take you to the most amazing places in the world. Whether it is your local diving spot 30 minutes away from home or across the world, there is beauty in every place if you know how to look for it. Keep your eyes and mind open, try new things, taste new foods and always ask for the local drink. It is all part of the adventure.

But the real magic, the things that keep me coming back for more happen underwater. Once you take the plunge (in this case quite literally) and this alien World unveils those marvelous things that only the ones brave enough to become divers can see is when it hits me, every time: Man, I am underwater, and breathing! How cool is that!

The feeling of weightlessness while wonderful creatures swim around you, the sense of harmony and peace that gliding through the water and the impression of flying gives always awes me.

The best diving memories I have are those of just being there…. Enjoying the beautiful natural environment full adventure, colors, discovery and friends some old, some new. Being together with other people who enjoy the underwater adventure, that like to brag about their diving exploits (yes, we all do it, come on admit it) and respect the environment adds a whole new dimension to this sport we call diving.

And that is why you always see me planning my next diving adventure, whether it will be in 2 weeks or 6 months. Because I am always longing for that time when I get to pack my heavy, heavy diving gear and drag it around for the next adventure.

-Stein

Diving safety series #2 – Signal Check

Scuba Diving GearThe ability to communicate is one of the main traits of the “dominant species” in this planet (whoever coined that term I am sure he did not dive!). Communicating with other people, is very important, but doing it underwater is crucial.

Unless you work diving missions for National Geographic or are filthy rich (and we all hate you for that… in a nice way of course!) and you have special gear that allows the use natural language while diving, you are limited to the use of hand signals to ensure you can efficiently transmit messages to your buddy and other divers around.

I am not going to review all the signals divers have at their disposal to transmit messages while underwater. For that, you can click here. However, I want to point out that it never hurts to go over a quick signal check to make sure that you and your buddy will be able to communicate while underwater. Specially if it is the first time you dive with that person.

Even if you have been diving with your buddy for some time, I have noticed that when more experienced divers do it, others in the group look at them and do it too. So, unknowingly you might be helping other divers.

.What I usually do is to go over the most important signals (no need to go over the entire manual again!). This is my short list of signals to check:

    • OK
    • Ascend/Descend
    • This depth
    • How much air do you have?/how to indicate remaining air
    • Something is wrong
    • Danger

I hope this little contribution encourages to perform a quick signal check next time you dive, and you never know, maybe by doing it, you are just becoming a safer diver.

Safe dive!

-Stein

Diving Safety Series #1 – Gear Assembly

Diving Gear One of the reasons people get into diving is because diving is a gear intensive activity. We love our gear!!! We talk about it, compare it and show it off (yes, we do, don’t give that innocent look). That is why when getting ready for a dive, one of the most important activities is the preparation of our gear.

I don’t think there is only one correct way of connecting and testing everything before we get all wet, every diver has his/her own methodology. but the important thing is to have one and follow it every time to make sure that all the pieces have come together properly all the time.

You would not believe how many times I had to stop some divers when they were about to jump into the water to connect the low pressure hose and (obviously) open the tank.

I want to share the procedure I use (ASSICOTT), hope it helps you. Also, if you have a question or suggestion to improve it (diving is an ever learning sport), please share it in the comments section of the post. I will be much obliged.

ASSEMBLING YOUR SCUBA GEAR (ASSICOTT)

  1. ALWAYS, ALWAYS assembly your own gear, don’t let anyone else do it for you
  2. Smell – let some air from the tank into your face and smell and taste it, if you detect any odor or flavor, DO NOT USE IT
  3. Secure – The BCD to the tank, once you feel happy with the set up, yank it a couple of times to make sure the tank will not slip out
  4. Install – Inspect the O-rings and install the 1st stage and secure it. Remember, don’t tighten all the way
  5. Connect – The low pressure hose to the BCD inflator
  6. Open – Take the console (SPG), face it down and away from you, open the tank, slowly. Note your tank pressure (typically 3000 PSI) and make sure you have enough air for the dive
  7. Test – Try the primary and secondary regulators, I breath (instead of purging) because that way I can check the mouthpiece is firmly placed
  8. Tidy up – Make sure no hoses are crossing, tangled or dangling

Now, also I recommend to extend this procedure with a quick check of other essentials:

  1. Straps – Check your mask and fins straps are in good condition
  2. Weights – Regardless of the type you use, make sure is secure and will not slip or come loose
  3. Zippers – Make sure all your zippers (Wet suit, boots, etc) are closed, all the way!!!

And remember, if you have a question or don’t know if something is properly assembled, ASK!!!! I bet you any experienced diver will be more than happy to show and teach you. Consider that NO ONE knows everything about diving.

BE A GOOD BUDDY

A final note, once you are ready, be a good buddy, inspect your buddy’s gear and have yours inspected by your buddy.

Happy and safe diving!

-Stein