An essential guide to buying a torch, by Matt Crowther and Steve Warren.

For novices and experienced divers alike, underwater lighting equipment has the same two simple functions: to see with and be seen by. And the wide range of activities available to divers today has resulted in an array of lamps from ‘gloom-busting’ exploration/video lights to low-power pocket torches. Divers often buy early on in their underwater career and give little thought to selection, or don’t have the knowledge to make a well-informed choice. Yet with a little research and care, it is possible to avoid the costly pitfalls that many people fall into. Above all else, consider the type of diving you do or plan to do and build around those requirements rather than choosing your equipment in isolation.

Light up your day dives

Beginners usually make their first dives in relatively shallow water and bright conditions. In such favourable situations, a dive light may seem unnecessary, but using a small torch will actually reveal ‘true’ colours, such as reds and oranges, which start to disappear as soon as you begin to descend. And you don’t have to go deep to discover undercuts, overhangs and holes in wrecks and reefs worth investigating – take a torch and you’ll find a wealth of marine life, including nocturnal predators such as eels and octopuses.

Your best choice of torch for this kind of diving is a small 2–4-cell light with a narrow beam for penetrating sunlit water and pointing into cracks and holes. It can be kept in your pocket until needed, hung from your wrist or pressure gauge or clipped into a holster on your leg, arm or belt.

Advanced diving needs

Many popular advanced diving activities – such as wreck penetration and deep, night and cave diving – require lights in order to see anything. In fact, with little or no natural light available, the diver’s lamp becomes an essential item of safety equipment. But choose carefully: torches with narrow beams reveal only small sections at a time, making it necessary to move the light continually, which gives a somewhat disjointed impression of your surroundings. Wide-beam lamps, however, powered by at least four D-size batteries or a single lantern cell, throw out an ‘umbrella’ of light over large areas. Cave divers insist on three lights for safety – a procedure worth considering in all circumstances where there is no natural light.

Talking by torchlight

In situations where underwater lighting equipment is a basic requirement for sight, an alternative to the usual system of communication is required. Fortunately, there are several universal ways of signalling with torchlight that anyone undertaking advanced diving should be comfortable with.

When natural light is poor, perhaps the easiest way of communicating with your buddy is to shine your torch towards your own body and, using your torso as a backdrop, make hand signals as normal under the light.

If you need to communicate with more than one person – perhaps another group of divers who are some distance away – using your torch as a giant pen to ‘write’ your signal is very effective. For example, by making a large circular motion, you can sign ‘okay’. This method is also good for on-the-surface signalling.

Torch safety

• Don’t make a light-dependent dive unless you’re formally trained in the appropriate specialised techniques.

• Always carry at least two lights – one for primary use, the other as back-up. But remember that back-up lights are escape lights: if your primary fails, use your back-up to surface safely, not continue the dive.

• Make sure each torch has a burn time longer than your planned dive time – and that includes enough time to make a safe exit from the water, not just to get to the surface.

• Whenever possible, try to have surface cover for the duration of any light-dependent dive.

• Always turn on your primary light before entering the water and leave it on until a safe exit has been made.

• Be constantly aware of other divers. Underwater torches are extremely powerful and can easily render someone temporarily blind.

• Always point lights in the direction of travel. For example, shine the beam down while descending, and towards the surface when ascending.

• If buddy separation occurs during a dive, cover your torch beam and look around for your buddy’s light. In very low visibility, however, it’s probably best to agree on immediate ascent if separated. At night, finding a torch beam on the surface is far easier than 15m down.

• As with all underwater communication, agree on appropriate torch signals while still on the surface.
  

Bulbs for dive lights are usually designed to provide a white beam which reveals ‘true’ colours and penetrates well underwater. Gases are often added to the bulb to increase performance: halogen is the best; krypton and argon are less effective but cheaper. Dual-filament bulbs are a good idea, as they provide an instant back-up in the event of one filament failing (flicking a switch brings the second filament into use). They can also be used to provide a choice of power settings while on a dive – switching to a lower power will increase your burn time.

Disposable alkaline batteries work well for occasional torch-users. Cheap to buy, they usually provide hours of burn time and do not require care and attention. Regular torch-users, however, will find rechargeable lights – although more expensive to buy – much less costly to run. Most lights use nickel-cadmium cells (NiCads), which can be recharged 500–1,000 times (care must be taken to run the cell down fully to ensure it retains a good burn time). A minus point is that NiCads work at full power for almost all their charge, then die with little warning. Gel cells, however, fade slowly, giving the diver plenty of warning that they’re running down. They can be recharged 100–200 times.

Most commonly used in small torches, smooth, or spot reflectors concentrate light on a finite area, allowing even low-power torches to produce a bright beam. For a wide beam, dimpled reflectors disperse light over a greater area but require more power. There are several styles of dimpled reflector available, so make sure you get

the most appropriate for your requirements: standard wide-beam torches use flood reflectors, for example, while video lighting requires high-quality, wide-angle reflectors to provide intense, even illumination and eliminate a sharp edge to the beam.

Grips

Small torches usually fit into the palm of your hand, requiring no separate handle. Larger lights often have pistol or lantern grips for easy carrying. If planning to dive in overhead environments, consider a grip that allows you to hold a penetration reel in the same hand.

Switches

Some lights can be switched on by simply screwing in the front to complete the electrical circuit. Avoid potential problems by turning the torch on and then screwing it back until the light just goes out before entering the water: upon descent, the increasing pressure will push together the two parts of the torch to form a circuit and the light will go on automatically. Direct switches use a simple lever sealed by an O-ring – one-handed operation is normal, although switches with safety locks (to prevent accidental operation) may need the use of both hands. Toggle switches are simply covered by a waterproof boot, but leakage can occur if the boot is torn or if it perishes, so keep an eye on its condition. Magnetic switches rely on two magnets working together to form a circuit: leakage isn’t an issue, but they can still fail.