One of the most important decisions to make is what equipment you need to handle out of air emergencies

Option 1 is not recommended at all. You'll find it difficult to persuade anyone to dive with you.

1. Single cylinder: one 10 to 15 litre cylinder, one regulator 
   • For: simple, cheap
   • Against: only one, single system - if it fails, you're totally out of air, must rely absolutely on buddy in an out of air emergency
2. Main plus pony: a 10 to 15 litre main cylinder plus a 3+ litre pony cylinder, each with its own regulator
   • For: two independent systems
   • Against: heavier, cost of pony cylinder and regulator, twice the cylinder testing and regulator servicing costs
3. Independent twin set: two independent cylinders each with a regulator
   • For: two independent systems
   • Against: heavier, cost of extra cylinder and regulator, many dive shops charge twice the price to fill for the same volume of air, twice the cylinder testing and regulator servicing costs, need to change regulators during dive to preserve safety reserve of air in each cylinder, possibility of accidently breathing a cylinder empty (leaving no reserve), does not work well with air integrated computers
4. Manifolded twin set: two cylinders each with a regulator, joined at the pillar valve with a manifold that has a valve separating the two cylinders. Keep valve open until an air loss occurs.
   • For: two independent systems, no need to change regulators underwater or balance air use from cylinders
   • Against: heavier, cost of extra cylinder and regulator, twice the cylinder testing and regulator servicing costs, danger of losing all air if the manifold valve cannot be closed when an air loss occurs, cost of the manifold
5. Single regulator manifolded twin set:  two 5 to 10 litre cylinders joined at the pillar valve with a manifold, one regulator 
   • For: simple, cheap
   • Against: only one, single system - if it fails you're totally out of air, must rely absolutely on buddy in an out of air emergency, old fashioned, twice the cylinder testing costs, cost of the manifold

Options 1 and 5 are not recommended for deco diving. They are too risky.

Option 2 has a small reserve cylinder. On the negative side: 3 litres is a small cylinder even for an emergency ascent.  On the positive side: it's normally for use only in an emergency, its likely to be full.

Options 3 and 4 have the potential for a larger reserve (and more safety). On the negative side: as both cylinders are generally used during normal diving there is the possibility of depleting the reserve before the emergency happens.

What cylinder size should you go for? 

For a first dive:

• 15 or twin 10 litre, 232bar : the standard
• 12 litre or twin 7 litre, 232bar : only if you have good air consumption or want to do shallower or shorter dives

For a second dive:

• 12 or twin 7 litre, 232bar : the standard
• 10 litre, 232bar :  only if you have good air consumption or want to do shallower or shorter dives

Twinsets are essential for deeper (say 40m+) and longer (say 40min+ bottom time) dives simply because the diver consumes so much air on those types of dive.

Minimum pony size : 3 litre 232bar - don't bother with anything less!

There are main 3 ratings of cylinders:

• 232 bar:
  • For: the most common, most compressors support 232 bar
  • Against: 77% the capacity of same size 300bar cylinder
• 207 or 227 bar:
  • For:  most compressors support these pressures
  • Against: older, these cylinders are often accidentally over filled to 232 bar because 232 is the most common pressure 
• 300 bar:
  • For: 29% more air in cylinder than same size 232bar cylinder
  • Against: heavier cylinders, denser cylinders (may not be able to use a weight belt - a valuable safety device),  even with 300 bar compressors you may not get the full 300 bar fill, difficult to get nitrox 300 bar fills, need to use 300 bar rated regulators and DIN fittings

There are main 3 types:

• A clamp :
  • For: simple, cheap, very widely used world wide
  • Against: maximum pressure rating 232 bar (or less for older cylinders)
• 232 bar DIN : (5 thread)
  • For: reliable, o-ring very well protected
  • Against: some countries don't have DIN fittings on compressors (take an adaptor), cannot be used with 300 bar cylinders
• 300 bar DIN : (7 thread)
  • For: reliable, o-ring very well protected, only way to use 300 bar cylinders, can be used for 232 bar DIN fittings too
  • Against: some countries don't have DIN fittings on compressors (take an adaptor)

If you think you may want to do deeper, longer and more demanding dives eventually, go for DIN from the outset - you'll save the money you would have spent converting everything from A clamp.

The main purposes of these are to provide :

• emergency buoyancy both underwater and on the surface 
• a platform for your aqua-lung and other diving equipment

There are main 3 types to choose from:

• Stab: 
  • For: fairly modern, high buoyancy, comfortable, some models used with twinsets
  • Against: expensive, probably will float unconscious casualty face down on the surface, some models not used with twinsets
• Wings: 
  • For: modern, very high buoyancy for technical diving, comfortable
  • Against: expensive, can float unconscious casualty face down on the surface, bulky, good for twinsets
• Adjustable Buoyancy Life Jacket (ABLJ):
  • For: unconscious casualty floats face up, cheap, light, small
  • Against: old fashioned, uncomfortable (strap between the legs), less buoyancy, unusual configuration for rescuer to understand, must buy a separate cylinder harness

The main purposes of these are:

• insulation from cold water
• protection from stinging animals (rare around Britain).

A side effect of suits is that they also provide buoyancy - a mixed blessing.

There are main 3 types to choose from:

• Dry suit: essential for all-year diving in Britain

  Seals at the wrists and neck prevent water entering the suit. Even so, you do get damp in a dry suit, mainly because your sweat cannot escape the suit.

  The suit has an air inflator and a air vent which allow the diver to control the buoyancy of the suit and to avoid "squeeze".

   

  • Membrane: you need to buy an under suit for insulation
    • For: Comfortable to put on and get off
    • Against: expensive, risk of unreliability because it's buoyant only if undamaged
  • Neoprene: 
    • For: built in buoyancy and some insulation in neoprene even if damaged
    • Against: difficult to get on and off, expensive, buoyancy and insulation decreases with depth

     

• Semi-dry: 

  Seals at the wrists and neck limit the volume of water entering and leaving the suit. You do get wet in a semi-dry suit but the water that enters is soon warmed up and does not leave the suit readily.

   

  • For: Cheap, simple
  • Against: Summer only, buoyancy and insulation decreases with depth

   

• Wet suit: 

  Wet suits are designed to be tight so that the volume of water entering and leaving the suit is small. You do get wet in a wet suit but the water that enters is soon warmed up and does not leave the suit readily.

   

  • For: Cheap, simple, protection from stinging animals
  • Against: Tropics only, buoyancy and insulation decreases with depth

Some under suits, in their efforts to resist water, are air-tight and can prevent air escaping through the dry suit air vent. This can cause the air in the dry suit to become trapped in the suit on an ascent and can result in a rapid ascent. 

To avoid this, puncture the under suit in the region of the dry suit vent and the tops of the shoulders to allow air to move more freely.

Gloves are needed for most British diving except in the middle of summer.

 They have two purposes:

• insulation from cold - the muscles in your hand have no power when they are cold
• protection from cuts and stings

There are two types:

• Neoprene - normal gloves manufactured in neoprene
• Dry gloves - consists of a membrane boundary with fluffy inner glove and a seal that prevents water getting inside 

Neoprene gloves should be tight fitting to bring the insulating neoprene in contact with your hands and reduce flushing warmed water out of the hood. 

Wearing gloves make you much more clumsy when it comes to adjusting or fixing equipment.

Wet gloves can be difficult to get on and off. Avoid this problem by wearing plastic diesel gloves (from service stations) under the neoprene glove.

Hoods are needed for most British diving except in the middle of summer.

They should be tight fitting to bring the insulating neoprene in contact with your head and reduce flushing of warmed water out of the hood. 

Its a good idea to puncture the hood with a knife 

• at the top of the hood, to let air out of a loose fitting hood
• at the ears of a tight hood, to avoid Inverted Ear pressure damage

The main purpose of a weight belt is to counteract the buoyancy provided by your suit. Another benefit of having a weight belt is the instant emergency buoyancy provided by dropping the weights.

• Quick release

Weight belts need a quick release mechanism so they can be dropped in an emergency. Don't be tempted, to avoid accidental loss, to attach the weight belt to your BC. A better solution is a secure buckle. Choose buckles that are difficult to open accidently but easy to open when required.

• Position of the belt

Make sure you put your dive kit on in such a way that you are able to remove your weight belt yourself in an emergency - the weight belt should not be trapped by other equipment. Weight belts always go around the outside (are put on after) fixed equipment like ABLJs.

Make sure the weightbelt is tight around your waist - loose belts do slip down over people's hips. 

• How much weight?

Do a buoyancy check in sea water to find out what weight you need. In a buoyancy check you test if you can maintain neutral buoyancy just below the surface with all your kit on - but all buoyancy devices fully deflated.

Try to reduce the weight on your weight belt to a level were you can comfortably maintain neutral buoyancy in shallow water with a nearly empty cylinder. 

A dry suit diver should need 6 to 10 kg of lead on the belt. If you use more than this, try to gradually reduce the weight over several dives.

• Excess weight on a weight belt can be dangerous:

• It forces you to inject more air into your suit or jacket to counteract the negative buoyancy - this makes a loss of buoyancy control more likely
• It makes you less able to stay underwater if you lose your weight belt accidentally. If you lose a light weightbelt you may be able to descend and get it - if you are unable to retrieve the weight belt, at least your rate of ascent will be less than if you had lost a heavy weight belt

• It's a good idea to secure the weights on the belt so that they cannot slip off when you hold the belt by the end that has no buckle.

• Shot weight belts are more comfortable on your hips than 2 or 4kg blocks.

• Some BC integrated weight systems overcome the two problems of the weight belt: they provide a secure way of storing the weights that can, at the same time, be quickly released. They have the disadvantage that your buddy, in an emergency, may not understand, see or use them properly.

The purpose of ankle weights is to lower the legs when wearing a dry suit. 

Too much air in the legs of the suit can cause the wearer to go upside down. As air can only escape from the arms and neck of a dry suit when it is upright, an inversion can lead to a rapid ascent.

At least three parts of your equipment should be brightly coloured:

• your hood: so boats and the surface cover can see you more easily 
• your fins: so your buddy can follow more easily
• the front of your suit and/or your gloves: having dark suit and gloves makes it difficult to read your hand signals in poor light

Light reflectors on your hood, shoulders and buoys are useful.

The best places to locate equipment are:

• where they can be seen easily
• are easily reachable
• can be quickly put to use

Generally that means right in front of your eyes in the triangle between your chest and your two hands when they are at your sides.

Here are some suggestions:

• Octopus demand valve: anchored on the front of the BC with a quick release clip. Not in a pocket or under your arm. Face the mouthpiece downwards to reduce freeflows.
• Computer or depth gauge: on a wrist where it can be read when both hands are full (as in a rescue). Console mounted instruments generally need a spare hand to be read.
• Knife: on the front of the BC with a lanyard attaching it to the scabbard and a rubber bungee securing it in place. Leg mounted knives may be out of reach. 
• Torch: on the front of the BC with a lanyard attaching it. 
• Deco buoy and reel: clipped in a BC pocket or clipped to the BC
• Compass: on a console (the hose must be long enough to centre the compass in front of you) or glued to a slate kept on a lanyard in a pocket
• Buddy line: clipped in a pocket.
• Whistle: tied to the BC inflation valve.
• Strobe: either tied to the BC near the shoulder or on the back of the mask strap. You must be able to switch it on, on your own.
• Flag: bungeed to a cylinder. You must be able to remove it on your own.
• Decompression table slate: clipped in a pocket.

The purposes of this class of equipment are to:

• allow your boat cover to find you on the surface after a dive
• prevent you being run over by boats on your ascent
• mark your position during a drift dive or while you're doing deco
• help lifeboats and helicopters to locate you

The group of equipment (with cheapest/most effective towards the top)  includes:

These are inflated on the surface before diving to mark the diver's position:

• during a drift dive so the dive boat can follow the divers
• where there is boat traffic (diving where there is heavy boats traffic is not recommended)

Here are some points to think about:

• A closed SMB, with a valve which you blow through, is likely to be more reliable (ie remain inflated) than an open ended buoy or a delayed buoy which seals its self as it inflates
• Identify yourself and your club on the buoy 
• To avoid losing the reel, it needs a lanyard to attach it to the diver:
  • this can either clip to the BC or go around the wrist
  • a lanyard of arms length allows the reel to float above the diver and stay out of the way
  • if the lanyard clips to the BC, take care to release if there are boats around (boats on the surface have been known to drag divers up by their SMB reels)

Deco(mpression) buoy (or delayed SMB) and reel

These are inflated underwater before or during the ascent to mark the diver's position.

• There are at least 3 types of deco buoy 
  • open ended (preferably with small independent weight to keep the opening submerged)
  • self sealing open ended buoys (the air in the buoy expands as the buoy ascends closing a neck at the bottom of the buoy)
  • closed buoys with a built in air supply and a pressure relief valve
• There are several common problems with deco buoys and reels
  1. The reel jambs after the buoy is inflated (dragging the diver up):
     • use a simpler system or a reel which cannot jamb (e.g. a weighted spool of line)
     • detach the lanyard connecting the diver to the reel before inflating the buoy (and ensure no equipment is trapped in the buoy or reel)
     • attach two reels to each other in series. If one fails the other is unlocked to reel out its line.
  2. Part of the diver's equipment gets trapped in the deco buoy (dragging the diver up):
     • tie the lanyard of the reel to something solid on the sea bed before inflating the buoy (so you have time to sort the problem out)
  3. To inflate the buoy, the diver removes the DV he is breathing from (and is therefore at a disadvantage in dealing with any other problems that might arise as the deco buoy goes off )
     • Use a deco buoy with its own air supply
     • Use an octopus DV to inflate the buoy

Masks

Masks can easily be swept off the face as you enter the water. They often do not float. Some people use neoprene straps that cause the mask to float.

If you wear glasses to correct your vision, you can have prescription lenses put in your mask by an optician.

Fins

There are several different styles of fin to chosse from, probably the most important things to take in to account is that they are comfortable to use and easy to put on.

The different fin styles are:

• Paddle fins
• Full foot fins
• Adjustable open heel strap fins

Paddle fins: Can be either full foot or have an adjustable open heel strap. For scuba diving purposes, most people use the adjustable heel strap fins. Full foot fins are commonly used for snorkeling and free diving. Traditional paddle fins work to move water up and down as you kick and are used by scuba divers when recreational diving or in currents.

• Split fins

Split fins: Some scuba fins are altered in some way with splits, cutouts or vents that the manufacturers say enhance the kicking force and efficiency. The majority of these are the split fins or "Bio-fins". These fins divide the paddle of the fin into two parts with a section taken out of the middle. This modification is supposed to minimize the number of kicks needed to cover a distance. The Bio-fin pushes water back instead of up and down and thus acts like a propeller instead of a paddle, allowing you to kicking easier and go further.

• Force fins

Force fins: This type of fin is considerably smaller than other scuba fins and they can provide equal kicking force. Force fins act like a small scale whale tail, which is some of the reason they claim to have successful kicking efficiency.

This group of equipment includes:

• Timers:
  • Watches
  • Bottom Timers - see Digital Depth gauges

   

• Dive Computers or Decompression Meters:
  • Air computers
  • Nitrox computers
  • Fixed ppN2 computers
  • Computers for Helium dives
  • Gas monitoring computers

   

• Depth gauges or Bottom Timers
  • Digital
  • Analogue

   

• Compasses
  • Magnetic
  • Fluxgate or electronic

These need to be very easily reachable and readable.