Underwater navigation is a skill that you will use on every dive, and not just an end to itself. To be a good diver, you must be successful at underwater navigation. Good navigation skills will take you where you want to go, to do the things you want to do. Similarly, night diving and limited visibility diving skills will help you achieve the things you want to do underwater.
To navigate underwater, or make night or limited visibility dives, you will need some additional pieces of gear beyond what you may already own. These items include a compass, an underwater light, a slate, a marker buoy, and other devices. You will find that you will use these items throughout your diving experience.
Below is a list of the most common equipment used during a night dive and its purpose.
The Mechanical Underwater Compass
You can purchase an underwater compass with a variety of mounting options. They can be mounted on your console with your other instruments. Wrist models are preferred by some divers, while others choose to wear theirs attached to their buoyancy compensator, using a spring loaded retractor.
Underwater compasses are usually made from rugged plastic. They will withstand a great deal of abuse, but should be treated with respect and care. A simple rinse with fresh water at the end of your diving day is usually all the maintenance most compasses require.
Take Notes on Your Slate
A slate is an indispensable piece of gear for all diving, but is particularly useful for activities like underwater navigation and photography. It is handy for taking notes and for communicating with your buddy underwater.
For dives where you are practicing underwater navigation techniques, a slate is essential for writing down compass courses, recording natural navigation features of the underwater terrain, and for triangulation, a technique for relocating dive sites.
If you use a flat slate, it can be attached to your buoyancy compensator, or stored in a pocket on your wetsuit or dry suit. Some divers also use round slates, that fit over their sleeves.
To clean a slate after you have written on it, run fresh water on the slate, sprinkle it with an abrasive cleaner, such as Ajax, and rub it with an abrasive sponge. You can also clear any marks on the slate using an ordinary eraser. Either way, the slate is ready to go back in the water immediately.
There are many different types of marker buoys available that are useful in marking a dive site or for practicing your underwater navigation skills. You can also make a simple buoy from items that are commonly available.
The two main categories of commercially available buoys for scuba diving are inflatable buoys and rigid buoys. Both types work well.
Inflatable buoys consist of some type of soft bladder, similar to a balloon. Two advantages of inflatable buoys are that they can be rolled up for storage and transport and inflated only when needed. This type of buoy typically uses a small CO2 cartridge for inflation. A line is fastened to the buoy on one end and to the object to be marked on the other end. This type of buoy requires a bit more maintenance than a rigid buoy and you must purchase a new CO2 cartridge each time you use it.
Rigid buoys are made from either hard plastic or from a non-compressible foam material. A small weight is usually attached to this type of buoy to offset its buoyancy and to serve as an anchor for the bottom end. Rigid buoys do not require any CO2 cartridge and are not prone to puncture. This type of buoy can be a bit more bulky to carry than the inflatable buoy.
To make a simple buoy for marking a dive site from the surface, you can use an old plastic bottle, such as a bleach bottle, nylon line appropriate to the water depth, and a two or three pound weight to anchor the buoy.
A dive light is one of the first accessories that most divers buy after their certification course. They’re not only useful at night, they’re also handy during the day, especially on deeper dives, to help restore the colors filtered out by the water. In California, most lobster divers carry lights even on daytime dives to help them look into holes and crevices while hunting for lobsters.
Dive lights differ from ordinary topside flashlights in that they have waterproof and pressure-proof cases and switches. They are much more rugged and are usually heavier than typical flashlights. Most dive lights today are made from either plastic or machined aluminum.
As battery and bulb technology has improved over the years, dive lights have gotten smaller and smaller. Although you might think a large light would provide more power and light, this isn’t necessarily true. Many of the smaller dive lights available today provide more than adequate light without the need for additional bulk or weight. In most cases, the smaller the light you can use, the better.
Any light you select for night diving should be a non-floating light, or should be easily weighted so that it will sink. Non-floating lights are preferred because if you need to set your light down on the bottom, you don’t want it to float away. If your light floats to the surface, and there is any surface swell or wind waves, you will probably lose your light.
Besides the traditional hand-held light, there are also head-mounted lights that provide a good alternative for night diving. Head-mounted lights are an excellent choice for the underwater photographer or hunter.
Every hand-held dive light should be equipped with a lanyard so that it can be worn on your wrist or attached to your dive gear. However, you must be able to easily remove the light in the event you need to remove it quickly in an emergency.
For night diving, it is recommended that you carry a minimum of two lights. They do not both need to be the same size. One light is used as your primary light and the second is used as your back-up light in case the first one fails.
Light Sticks and Marker Lights
Light sticks are small lights that are designed to attach to a diver’s snorkel or tank valve to identify their location, both on the surface and underwater. Relatively inexpensive Chemical light sticks are available. These devices consist of a heavy walled plastic tube with an inner cylinder of thin glass. The outer plastic tube and the inner thin walled glass tube contain two different chemicals. Chemical light sticks are also known as “cyalumes.”
When the plastic tube is bent, the glass tube breaks and the chemicals mix together. Once the chemicals mix, they emit a bright glow that lasts for several hours. Chemical light sticks can be attached to a diver’s snorkel using waterproof electrical tape, or tied to the tank valve or regulator first stage using a bit of string. In recent years, chemical light sticks have lost their popularity with some divers who feel they are not as environmentally friendly or economical as reusable battery powered light sticks.
Battery powered light sticks are also available and these work well, too. These devices function like a small flashlight, except that the bulb is encased in a plastic shroud that is completely transparent, so the light can be seen from any angle. Battery powered light sticks are reusable by simply replacing the batteries when they lose power or the bulb when it burns out. If you night dive on a regular basis, a battery powered light stick is more economical than a disposable chemical light.
Marker lights or “exit lights” are used to help you relocate the anchor line underwater if you are diving from a boat, or to help you relocate your entry point if you are diving from the beach. There are many different types of marker lights that work well, but it’s a good idea to pick something distinctive, like a strobe or a light with a colored lens, that is easy to identify compared to any other lights that may surround it.
Sound Signaling Devices
For night diving, it is strongly recommended that you carry some type of sound signaling device for getting the attention of the boat operator if you are swept away by a current and your light is not working. This can be a whistle or an air powered horn that works off the low pressure air from your regulator.
Retractors are small spring-loaded mechanical reels that are used to attach dive accessories to your buoyancy compensator. They can be used to attach lights, gauges, slates, and other accessories. When you pull the accessory away from your body, the retractor unspools the line and when you release the accessory, the retractor automatically reels it back in out of your way. Retractors are invaluable accessories for carrying your spare dive light or slate.
Electronic Navigation Aids
The number of electronic aids that can assist you in underwater navigation continues to grow each year and their capabilities are astonishing. The most popular electronic aids are dive tracking devices, electronic compasses, and underwater sonar. For divers who need extremely precise locating capabilities, underwater GPS (Global Positioning System) is also available. Although underwater GPS systems are currently priced out of the range of sport divers, there is no doubt they will be commonly available in the future.
Dive tracking devices are designed to help you relocate the boat or a site that you have marked. The system consists of two devices; a sending unit that emits an electronic signal and an electronic receiver. The sending unit can be hung over the side of the boat, attached to the anchor line, or attached to a wreck or other underwater site. As long as the sending unit is on and has battery power, it gives out a continuous directional signal that can only be picked up by the receiver.
To use the receiving unit, the diver turns on the receiver and swings the unit as he turns in a circle. When the receiver is pointing directly towards the sending unit, the display indicates the correct direction and distance. These are very simple units to use and make underwater navigation extremely simple.
Electronic compasses extend the capability of the ordinary magnetic compass. They perform course calculations for you automatically, and are much more precise than traditional mechanical compasses.
Underwater sonar units are used primarily to measure distances to large objects in limited visibility. These systems are helpful in locating wrecks and reefs.
The Global Positioning System, or “GPS” as it is more popularly known, is a system designed by the U.S. military, using satellites to help locate positions on Earth. A series of satellites in orbit around the earth each send out a signal that can be picked up by GPS receivers. The receivers interpret the signal from each satellite and, by mathematical calculation, provide the location of the receiver.
When people say they own a GPS, they actually mean they own a GPS receiver. GPS receivers are widely used topside, and are quite inexpensive and simple to use. You may have the opportunity during your navigation course to see how GPS operates, particularly if you do any of your diving from a boat.
Some dive boats are still equipped with LORAN, which is an acronym that stands for Long Range Navigational system. LORAN is a good system that has been used for many years, and also provides accurate navigational information. LORAN works in a similar fashion to the GPS system, but the transmitting stations for the LORAN system are located on land rather than in space.
Divers use LORAN and GPS systems in conjunction with a depth finder (fathometer) to position themselves on a dive site. Once the boat is anchored close to the correct spot, depending on the size of the site, you may still need to search for it underwater.
Full-Face Masks and Wireless Communications
Two additional items that can be of tremendous value during many diving activities, but especially in night and limited visibility diving are a full-face mask and wireless communications. The full-face mask is a diving mask that covers the eyes, nose, and mouth. Wireless communications are electronic devices that capture human speech, transmit them through the water as an electronic signal, and reconvert them to a sound you can hear. These two pieces of gear, working together, will allow you to communicate without the need to see your dive partner face-to-face. In certain situations, this type of equipment could save your life.
Full-face masks are not difficult to use, but they do require some additional training before you can use one properly in open water. Ask your instructor about additional training in this specialized equipment.
Since there is no place to stop and ask directions underwater, we hope that this article will be a valued reference to make sure you end up where you wanted to and come back safely.
For more information on the necessary equipment for night diving or to inquire about furthering your diving skills, contact your local SDI Dive Center.
Contact SDI TDI and ERDI