Scuba diving equipment

There are a few key pieces of equipment that required for any dive, and some other equipment that is used for more challenging diving conditions.  Beginners and novice divers, however, will definitely need the following:

Mask
The human eye cannot see clearly through water so a pocket of air is    required to maintain vision when diving.  A diving mask is like a large pair of swimming goggles with a silicone seal all the way round.  It also includes a silicone pocket/seal for the nose, to prevent the wearer inadvertently trying to breathe through their nose and sucking in water instead.  Diving masks are built to withstand the greater pressures found underwater, so a snorkelling mask is not suitable for diving.

Fins

Divers get quite shirty if you refer to fins as “flippers”, so be sure to get your terminology right!  Physical effort, such as swimming, uses energy and to fuel that energy oxygen is required, which is why people breathe more heavily when doing exercise.  Underwater, the diver wishes to conserve energy to make the air in his cylinder last longer.  Fins, therefore, are used to make swimming underwater as effortless as possible.  Fins are large, flexible blades attached to the feet, which provide maximum propulsion through the water for minimum physical effort.  There are two basic types of fins: shoe fins fit onto the bare foot like a slipper, strap fins have a foot pocket with a strap that fits around the heel and are worn with boots.

Protective Clothing
Even in warm water, some form of protective clothing is required.  There are four main types:-
•    A skin suit is a thin layer that just protects the body from abrasion, either from the equipment worn or from brushing against rocks, corals etc.  A skin suit is only worn in the warmest water.
•    A wet suit provides some thermal protection as well as protecting against abrasion.  Wet suits are available with long or short arms and legs and in a range of thicknesses.  Made of neoprene, a wet suit allows water to flush through it, holding a thin layer next to the skin, which the body warms, providing some defence against slightly cooler water temperatures.
•    A semi-dry suit is rather like a wet suit but has seals around the neck, wrists and ankles.  Water ingresses into the suit and is then trapped there to be warmed by the body.  A semi dry suit offers greater thermal protection than a wet suit.
•    A dry suit is used for cold water diving and allows no water to ingress at all.  A dry suit has built in boots and seals around the wrists and neck; inside the suit the body stays dry.  Additional thermal protection is worn underneath a dry suit, in the form of warm under layers.  Dry suits are made either from neoprene or a trilaminate membrane; neoprene suits tend to be slightly warmer than membrane, although membrane suits allow greater freedom of movement.  When diving in cold water, neoprene hoods and gloves are usually also worn for warmth.  Special training is required before diving in a dry suit.

Buoyancy Compensation Device
There are several types of buoyancy compensation device (BCD), variously known as BCDs, BCs (buoyancy compensators), stab (stabilizer) jackets and wings.  All work in the same way.  The BCD is worn like a jacket and consists of internal air bladders, a hose for adding or extracting air from the bladders, a loop system for holding an air cylinder and usually some pockets and D-rings for holding other pieces of equipment.  The air that is added to or taken out of the internal bladders controls buoyancy underwater and the rate of descent and ascent to and from the surface.

Weights
A human being is naturally buoyant, and even when carrying a heavy dive cylinder will not automatically sink under the water.  To counteract this natural buoyancy, therefore, divers wear lead weights, either on a belt, in a harness or in the pockets of their BCD.  Whilst underwater a small amount of air is added to the BCD to keep the diver off the bottom, or at the depth they have chosen, and whilst on the surface the BCD is filled with air to counteract the negative effect of the weights.

Cylinders
Contrary to popular belief, diving cylinders to do NOT contain oxygen, they contain air.  The air is compressed and held in the cylinder under pressure (measured in either pounds per square inch (psi) or bar) by a valve on the top.  Cylinders are usually made of steel or aluminium and come in a range of sizes, measured in cubic feet or litres.  The advantage of a larger cylinder is that it contains more air, and therefore the diver can stay underwater longer; the disadvantage is the heavier weight.  All diving cylinders must be periodically inspected and tested by independently accredited testing facilities to ensure they are safe.

Regulators
Regulators, often referred to simply as “regs”, are more properly called “a set of regulators”, since there are several component parts.  The air in the cylinder is held at very high pressure, which a human being cannot breathe, so the “first stage”, which includes a clamp that attaches to the cylinder, reduces the pressure of the air to around 140psi/10 bar above ambient pressure (ambient pressure increases with depth).  Attached to the first stage are a series of high pressure hoses.  In a typical set up for a novice diver, one of the hoses will be the “feed” for the BCD, one will accommodate the mouthpiece (or “demand valve”), one an alternative air source (also known as an “octopus”) and one a contents gauge.
•    The Demand Valve (DV) delivers breathable air to the diver via a mouthpiece.  The DV reduces the air pressure further to match the ambient pressure. The diver breaths in and out through the DV, the exhaled air being expelled through an exhaust on the DV, producing the characteristic bubbles associated with breathing underwater.
•    The octopus is a second DV to be used by a diving buddy in the case of emergency.  It is usually bright yellow in colour for easy identification underwater.
•    The contents gauge shows the diver how much air is left in the cylinder and is usually a round dial with a needle to point to the appropriate level.  Sometimes content gauges can be combined with other instruments in a console, which might include a depth gauge and/or a compass.

Computer
Nearly all modern divers use a computer.  The computer is worn on the wrist like an oversized watch and has many functions.  The computer will tell the diver his depth, how long he has been diving and how long he can remain underwater without the need for decompression stops on ascent.  It also measures the rate of ascent back to the surface (it is very important to control this as ascending too quickly can cause decompression sickness, also known as “the bends”).  The computer has other functions such as calculating decompression stops and some can also be used for accelerated decompression using a mixture of breathing gases, but these are advanced techniques and therefore need not concern the beginner.

IMPORTANT NOTE
It is IMPERRATIVE that anyone considering scuba diving undertakes proper training with a recognised training body.  None of the equipment mentioned in this article should be used without instruction.  With proper training, scuba diving is a fun, exciting, pleasurable hobby; without, it can be very dangerous indeed.