What’s S.C.U.B.A?

For those who aren’t exactly clear on how it is that almost 10 million people a year are able to spend hours at a time underwater, here’s a quick run-down on how it works and some of the equipment involved:

S.C.U.B.A stands for …    

Self
Contained
Underwater
Breathing
Apparatus

…and has been around for ages in a number of forms. However, Jacques Yves Cousteau and Emile Gagnan modified it to its current configuration with the invention of their ‘Aqualung’ in 1943. Today when we speak of scuba, we are typically referring to an in-line, open-circuit system which is used with a compressed air cylinder to supply air to a diver at a comfortable rate when the diver ‘demands’ it (by inhaling).

Scuba Tanks

Scuba tanks, or cylinders, are usually made from either an aluminum alloy or steel and come in standard sizes ranging from 1-15 liters depending on how they will be used. For recreational scuba diving such as what we do on Koh Tao, we typically use 12 liter aluminum (note- Gary is an English Chemistry major and swears it’s alumin-I-um, whereas Darius is American and is certain  it’s aluminum, guess who wrote this section…) tanks filled to a pressure of 200 bar. So, when you dive with a full 12-liter tank on your back, you have the equivalent amount of air of 200 12-liter tanks compressed into a single ALUMINUM cylinder.

Regulators

The next step is taking that tank pressure, which is very high, and delivering it to you at a pressure which is equal to the pressure at the depth where you are diving. This is accomplished through the use of Mr Cousteau and Mr Gagnan’s contribution to scuba diving- the regulator. This strange looking compilation of metal, rubber and silicon attaches to the tank and has a number of components such as:
 
     - a First Stage, which reduces the high pressure from the tank to an intermediate pressure for  
     delivery to a Second Stage via a reinforced hose.

     - a Primary Second Stage, which takes this air at intermediate pressure and further reduces it to
     the surrounding pressure allowing for easy delivery when the diver inhales (thus, we call it a
     ‘demand valve’ system).

     - an Alternative Air Source, or Octopus, which allows for a second diver to breathe off the same
     scuba unit in the event of an equipment malfunction or out-of-air emergency.

     - a Low Pressure Inflator Hose, which attaches to your BCD (jacket) so that you can pump up
     or release air to help adjust your position in the water and achieve what all divers aspire to-
     Neutral Buoyancy. You can also add air to your BCD by blowing air from your lungs.
     
    - and finally, the Submersible Pressure Gauge (SPG), which monitors the air pressure in the tank
     and allows you to adjust your depth and dive time so that you don’t run out of air underwater.

There are a lot of variations on regulator design and types of scuba. Open circuit refers to the design in which exhaled air is released into the water and no gas is re-used. Semi-closed and fully closed circuit scuba systems actually recycle the air, remove some of the exhaled carbon dioxide from it and inject it with oxygen so that it can be ‘re-breathed’. This is useful for technical diving which allows for longer dives because of an increased air supply. It also allows you to get closer to the marine life as there are little or no noisy bubbles.

Buoyancy Control Device

The Buoyancy Control Device (BCD) is basically an inflatable jacket which your tank is attached to. As you change your depth and breathe air from the tank, you’ll find that your buoyancy will change- you’ll have a tendency to either float or sink. The BCD allows for you to adjust your buoyancy by either putting air into, or releasing air out of your jacket so that you can become neutrally buoyant and move more easily through the water.

Together the Tank, Regulator and BCD, once assembled, is referred to as your Scuba Unit.

Weightbelts

I’m not being funny, but there’s not really a lot to say here. It’s a belt… with weights. They make you sink and are used in conjunction with the BCD to adjust your buoyancy in the water. You’ll find that as you become better and better as a diver you’ll require less and less weight on your belt, meaning that you’ll move easier through the water and use less energy and air.

Masks

As you probably know from the swimming pool, you can’t really see that well underwater. For this reason, we wear a mask which allows for an air space between our eyes and the water, bringing things into clear focus. A comfortable and well-fitting mask is one of the cheapest and most important bits of diving equipment, and can also serve a dual-purpose as you can use it when you go snorkeling from the beach on the days off from your internship. This is also a great way to meet people on Koh Tao!

Fins

Fins help us to utilize our large leg muscles to propel us through water rather than our relatively small arm muscles (no offense to Gary). A comfortable fitting pair of fins is a must for scuba diving and again is useful on those days off for exploring the shallow reefs just offshore. There’s a huge array of fin styles to choose from and Gary and I will be happy to help you select a pair once you’re here.

Wetsuits and Rash Vests

Because water is so much more dense and conducts heat so much more efficiently than air, divers tend to get colder quicker underwater. A wetsuit actually works on the basis that it slows the water movement across your skin, thereby keeping you warmer. As the year-round water temperature on Koh Tao rarely dips below 28C, divers here mostly use just a short 3mm thick wetsuit (Shorties have short legs and arms, duh!) which is typical for a tropical environment. Oftentimes, people coming from a cold water climate are more than happy wearing only a rash vest- the same as surfers wear only they call them ‘rashies’ in their hip surfer lingo- just to keep the skin from rubbing against your equipment and causing a rash (Get it? Rash vest…).

Dive Computers

Dive computers are quite common in recreational scuba diving today because they help to speed up dive planning and are a great way to monitor things like depth, air supply, and they can help you stay within your dive limits. There are a wide range of computers on the market today that are used for many types of diving. It’s good to find a dive computer that you can more-or-less grow into, that is, one that has a few functions that you may not need in the beginning but can be useful as you become more advanced as a diver. Again, Gary and I are more than happy to help you select a computer once you arrive and have gotten a better idea of what kind of diving interests you most.

These are just the basic bits of equipment that all divers will use. However, there’s a wide range of accessories like dive knives, underwater torches, signaling devices, bailout tanks and more that you’ll find useful in the future. All of our packages include everything you’ll need for your courses and also are flexible so that if you care to upgrade any piece of equipment, you have that option.