Know how a set of scuba gear works? Here's a free lesson from DJL!
First things first. What does scuba mean?
I.e. something that you can take underwater and breathe from.
So what are the essential components of a basic scuba system?
Scuba Diving Cyliner (or Tank)
We need a supply of air to breathe underwater, so we carry a cylinder (or tank) on our back.
These come in a variety of shapes and sizes, but we normally use a 12 litre cylinder pumped 200 times higher than atmospheric air pressure (200 bar).
Regulator First Stage
200 bar is way more pressure than we can breathe in. What we need is a regular set to reduce this pressure to that of the surrounding water pressure.
The first part of the regulator set is called the first stage. This is a precision (expensive) bit of engineering which reduces tank pressure way down to something called the intermediate pressure, which it feeds down to the . . . .
2nd Stage or Primary
This is the bit that we put in our mouth and breathe from.
The second stage contains a diaphram which fine tunes the intermediate pressure to the surrounding water pressure.
Most people are amazed how easy it is to breath from a regulator when they first start diving - there is basically no noticable breathing resistance thanks to great modern engineering.
Alternate Air Source (or octopus)
In case our buddy has any difficulties, or stupidly runs out of air (which should never happen), we have another second stage running from our first stage.
This redundant second stage is called the alternate air scource, and means in the event of an emergency we can share air from our tank with another diver.
This makes diving very safe, and is one of the reasons why we always dive with a buddy.
Buoyancy Control Device (BCD)
To attach the tank to our back we use a kind of inflatable jacket called a BCD.
The BCD is useful because we can control the amount of air inside the jacket, thus can control whether we float, sink or hover motionlessly in mid water.
Low Pressure Inflator Hose
Rather than inflating the BCD manually by using air from our lungs, we can save effort by using tank air.
The low pressure inflator hose allows us to connect our regulator to our BCD, so we can use buttons on our BCD to control our buoyancy.
Takes a bit of practice to get it right!
Since our eyes can't focus underwater, we need to wear a mask.
They come in a variety of shapes, sizes and colours. Tim likes wearing his special pink mask.
A scuba diving mask has to have a nose pocket to allow you to pinch you nose and equalise your ears during descent (similar to on an aeroplane).
With all this equipment strapped to your back, it takes more effort to get around underwater.
To compensate this we use long powerful fins, that take the effort out of diving.
The best type are large, rigid full foot fins that you wear together with a wetsuit boot.
Obviously we need to monitor how much air remains in our tank. For this we use a submersival pressure guage or SPG. We normally start our dive with about 200 bar - we always keep a reserve of 50 bar, so this gives us about 150 bar to work with. This means we can dive for about 45 minutes if we go down to 20 metres.
The second instrument on our console is a depth guage, so we can always keep an eye on our depth.
It's also a good idea to know where you are going underwater.
Sometimes visibility can be low - we can never see as far underwater as we can in air, because there are lots of suspended particles.
The best solution is to use an oil filled compass, so you always know what direction you are travelling in.
Our body looses heat twenty times faster in water than in air. This means we need to wear an exposure suit to make sure we don't get cold.
Around Koh Tao, the water is normally around 30°C, i.e. a warm bath.
We can therefore use a 3MM neoprene shorty wetsuit to make sure we are adequatly protected.
The down side of wearing a wetsuit is that it makes us float.
To compensate we wear a lead weight belt, enabling us to sink at the start of the dive.
When we reach the depth that we want to stay at, we add a little air into our BCD to achieve neutral buoyancy.
Although not essential, a dive computer combines a lot of information in one place, and makes diving a lot easier.
You have your depth, bottom time and remaining no decompression time (or deco data) all on your wrist. You can even get models with digital compasses and integrated air transducers.
If you have any spare money, buy a dive computer. We have a selection in our shop on Koh Tao Thailand, (very reasonably priced)!