Night diving requires the use of specific equipment in addition to the standard daytime diving equipment, for both surface support personnel and divers.
The light sources that are normally used are the Flashlights and Lights that the diver carries to illuminate the environment that surrounds him, the Sticks and the Mini Flashes that are used to signal both the location of the diving companions and the Strobe lights that are used to mark the boat or the entry / exit point.
Strobe Lights
If you conduct a night dive from the shore, you will need to leave signal lights at the point of entry to indicate the point of exit.
The best way to do this is to place two lights at different heights at the point of entry, vertically one on top of the other. When returning to shore, swimming on the surface, line up the lights vertically and swim towards them. Keep the lights vertically aligned as you swim.
On the surface, existing lights can also be used as a reference, such as lights or public lighting beacons (usually placed in a raised position), to which a lamp placed on the ground can be aligned with the point of entry to the water.
In the case of shore diving, it is strongly recommended to use a diving buoy to mark the point where the descent begins, which will also serve as a reference for the ascent.
Strobe Lights (commonly called “Strobes”) are used to mark the entry and exit point underwater. They are equipped with a bulb that emits a very bright and intermittent light and are placed in the water by divers at the start of the descent and fixed just below the surface near the entrance or at the end of the marker buoy.
Do not use strobes outdoors as this type of signaling could be confused with other navigation signals.
At night it is easy to lose your bearings, so a reference light even when diving from a boat is very helpful; in this case, the flashing light is fixed to the anchor line or to a special descent line so that the diver can easily find his way back.
The strobe light is a very important reference point, the less experienced, for example, will be able to dive while remaining in sight of the flash emitted by the strobe and have the peace of mind of knowing exactly where the exit line is located.
UNDERWATER LIGHTS
Underwater divers lights, or flashlights, serve as the primary tool for the diver to illuminate the area around him. Each diver must be equipped with two dive lights, a primary dive light, and a backup or secondary light.
The backup light is for use in case that the primary light fails during the dive, or if a member of the dive team loses all of their lighting sources.
Underwater dive lights come in a wide variety of choices, with different characteristics to fit different types of diving.
However, the two primary considerations should be whether the light runs on rechargeable batteries, or disposable batteries, and the illumination source.
Lights with rechargeable batteries are often more expensive at the time of purchase, but save on the additional cost of replacements disposable battery. Disposable batteries need to be replaced every time you go on a night dive. It is important to remember not to leave them inside the flashlight after diving, as they could cause a gas leak which can result in difficulty in opening and subsequent damage to the flashlight.
Therefore, by using rechargeable batteries you will be directly contributing to the protection of the environment. Moreover, since the recycling of disposable batteries is expensive and damaging to the environment.
Another characteristic is the type of flashlights used:
The Halogen Bulb is a bulb equipped with a tungsten filament that when it becomes incandescent emits light. This light reaches a higher temperature than a traditional incandescent bulb and emits much more light. Powers ranging from 20 to 100 Watt are generally used for underwater flashlights. The more powerful the bulb, the more battery packs are required and these must be adequate to guarantee sufficient autonomy: a good solution is to use 50W lamps where it is possible to obtain a use of 50/60 minutes with medium sized batteries. Advantages: excellent color rendering, low cost, good strength and durability. Disadvantages: low battery life and/or large, heavy battery packs.
HID (High Intensity Discharge) Lamps, that is, high intensity discharge, do not have a metallic filament and the light is produced by a continuous electrical discharge between two electrodes surrounded by a gas, generally Xenon. To generate the initial discharge, a voltage of tens of thousands of volts is required, so they must be controlled by a special electronic component that is subsequently responsible for reducing the voltage and stabilizing the light. Advantages: bright light and good autonomy. Disadvantages: very high cost, sensitivity to shocks and repeated turning on and off. Until a few years ago they represented the only alternative to halogen lamps and for this reason they have had a moderate acceptance, especially in technical diving, despite the great limitations that we have just seen.
LED Lamps efficiently use the optical properties of semiconductors to produce light: the term “LED” is an acronym that stands for “light-emitting diode”, that is, “a diode that emits light.” LEDs take advantage of the optical properties of some semiconductor materials to produce photons (in the visible or infrared band). When using an LED, it is always necessary to have electronics controlling it to limit the current and keep it within the allowable values to prevent the LED from burning out. Unlike what is commonly believed, LEDs also produce heat but retain it inside and must be carefully designed and mounted to dissipate, especially the high power ones typically used for underwater lights, otherwise the LED itself would be destroyed. LED lamps have many advantages: long lasting, given by low consumption, resistance to shocks and vibrations (there is no filament that can break), excellent resistance and duration (50,000 hours versus 1000 hours of a halogen), high efficiency, wide range of colors available and small dimensions. Disadvantages: medium cost, requires electronic control, not very high unit power of a single LED (to obtain high emissions it is necessary to couple more LEDs and precisely focus the light of all of them to obtain a uniform beam). It must be said that LED technology is evolving very rapidly and more and more powerful LEDs are being introduced to the market.
Now that powerful LEDs are a reality, HID is a technology destined to reduce in use, or to disappear, at least in the underwater world, as it happened to the halogen flashlights which was the most used until the beginning of the first decade of 2000’s.
In order to compare light sources, it is necessary to understand the meaning of some terms by identifying their characteristics: Watt, Lumen and Lux.
Watts represent energy consumption and, we must remember that the more powerful a lamp, the more energy it consumes (with the same battery it looses its charge sooner), and they are often taken as a reference to measure its efficiency, but each light source has a different performance, a different spectrum, different light temperature, and each lamp has a reflective cone with a different angle of emission; comparing them in watts therefore doesn’t make much sense.
Lumen is the luminous flux emitted per unit of solid angle (a cone of one degree) and therefore represents the luminous intensity of a lamp: essentially it can be said that two light sources that emit the same lumens are equally powerful. This does not mean that the light beam of two flashlights with the same lumens is the same because there are other factors that intervene: the characteristics of the reflective surface and the lens, the width of the emitted light cone, the color temperature of light (our eye mostly perceives yellow-green light).
Lux is also a measure of light but instead of measuring the light emitted at a certain angle, as the lumen does, the lux measures the light power on a surface, 1 lux equals 1 lumen per square meter/ 3ft sq. With the same lumens emitted and at the same distance from a surface (for example, one meter), a flashlight with a wider beam produces less lux than a lamp with a concentrated beam despite having the same light output. So if the angle of the light beam and the illumination distance are not known, even the lux has a very relative meaning when evaluating the power of a diving flashlight. As a reference, it may be useful to know that the light of the full moon reaches a maximum of 1 lux, the sun at sunrise or sunset reaches 400 lux, on a cloudy day it reaches 1,000 lux and on a clear day the illumination from the ground is between 30,000 and 100,000 lux.
Prior to buying a dive light, make sure that it is manufactured expressly for underwater use, and that it is not simply a waterproof light, one that is resistant to water, but not to pressure.
When you are ready to purchase a dive light, talk to your local dive shop, they are the professionals regarding such equipment and will help you choose a light that best suits your needs from the many options they have available.
Individual Marking Systems
Some divers also use a light attached to the tank’s valves, which is used to indicate their position to fellow divers.
Often, unfortunately, disposable chemical lamps are used which are constructed of a flexible plastic tube inside with a small vial with two chemicals that once mixed after the tube breaks after bending it, the mixture emits a chemical luminescence, producing a diffused colored light.
SNSI opposes the use of chemical lights such as these products meant for a single use. They are not easy to dispose of and are harmful to the environment. There are special lamps on the market known as Stick Lamps, small and colored, battery equipped that function perfectly and do not contaminate the environment. In addition they can be used numerous times. Furthermore, the batteries can be recycled. Another alternative can be the colored Mini Flash Lamps, equipped with a wet sensor that turn on as soon as they come into contact with water and turn off when they dry. But even in this case, once the small battery runs out, they need to be recycled and replaced.
Every diver should be aware that the enjoyment of their fun is the aquatic environment, which is very delicate and sensitive to pollution. Each of us must feel the responsibility and make a commitment to do our very best to reduce the impact of our presence in the underwater world. If you have not done so yet, you can ask your SNSI Instructor for information and enroll in the SNSI Ocean Guardian Specialty course that will make you a conscientious diver capable of contributing to improving and caring for the planet. Even small daily actions can have large results, it will make you a responsible and attentive diver, ready to be an Ocean Guardian of the aquatic environment.
MAINTENANCE
Whichever type of flashlight you choose, you should always ensure good maintenance for this type of equipment. Underwater flashlights and lights are designed and manufactured to minimize the risk of failure and exclude corrosion, using special materials and surface treatments for their construction. However, proper maintenance can increase its useful life.
After each ocean dive, always rinse the external parts with fresh water, preferably slightly lukewarm, while moving the parts such as the safety lock or the on and off switch. This operation allows it to completely eliminate the salt residues accumulated on the surface of the flashlight and in its external cavities. Before removing the battery recharging cover or opening the flashlight compartment, you must dry it completely to prevent water from entering.
Other elements to be treated with care are the “O-rings”: before replacing the refill cap or closing the flashlight compartment again, it is necessary to check that they are in good condition and make sure that they are cleaned and lubricated with silicone grease (free of hydrocarbons) to avoid water seepage inside the flashlight and causing damage to the electrical parts and / or the lighting system.