Chapter 8- Limited Visibility and Night Diving Limited Visibility and Night Diving 213 couple of extra battery packs to sustain you on vacations where night dives come in multiples. Dive Light Maintenance The primary cause of a flooded light is an improperly seated o-ring. You should take extra precaution to seal the light in a well illuminated area. Preferably, do it before you dress to dive. Check and carefully clean the o-ring. Apply a light film of silicone grease to the o-ring. Be sure all wires, grit, or other foreign matter are clear of the sealing surface. Carefully screw down the lens or snap the sealing latches evenly. Examine the look of the light to assure that everything seems even, flush, and properly positioned. If you can see the o-ring, it should appear as a solid black line. If a light is flooded with salt or fresh water it often can be salvaged. Open up the light, pour out the water, and flush liberally with fresh water. If the batteries are disposable, remove and discard them. Allow all pieces to dry, or use a hair blow dryer to speed drying. Look for the source of flooding, such as switches, o-rings, or cracks in material. Replace o-rings or repair the case as needed. Reassemble the light and test for leaks. Avoid banging the light unnecessarily, especially when it is turned on. Impacts tend to make the bulk filaments fail. Use a rubber strap to retain the light on your wrist. Occasionally, you may need to have your hands free to deal with an equipment problem. Ni-cad batteries may have to be recharged many times to reach full capacity. Following extended storage, the battery pack will have to be recharged to full capacity. If the batteries are discharged to the same point many times in a row, they will develop a memory, which reduces the light’s burn time. This memory can be erased by running the battery down to near exhaustion, and then recharging. Chemical Glow Sticks Another essential piece of equipment is a chemical light stick (Cyalume®), or a small single-battery marker light (figure 8-7), attached to your gauge console or cylinder valve to make it easy for you and your buddy to FIGURE 8-7. BATTERY-POWERED MARKER LIGHT keep track of one another. They can also be used as a backup for signaling in case the primary light fails. The tube contains two separate chemicals. When the tube is bent, thin glass inside breaks and allows the chemicals to mix, which produces a glow that can last several hours. They are available in a variety of sizes and colors, which can be useful for identifying different groups of divers,or dive leaders. Strobe Lights Strobe lights (i.e. compact, high-intensity flashing lights) are available for emergency signaling at the surface. They can be seen for miles and are more likely to attract attention of persons on shore. They are small enough to be carried in a BC pocket. They can also be used under water to mark the anchor or anchor line of a boat. Surface Lights In addition to dive lights, you will need lights for above water use. These include lights to use for dive preparations as well as surface lights to mark the entry/ exit location. It is a good idea to use regular flashlights for above water use. This conserves the batteries and bulbs in your dive lights. Also, some dive lights will overheat unless cooled by immersion in water. It would probably be wise for your flashlights to be waterproof in case they fall in the water. Lights to mark the entry/exit point can be anything from a lantern to a flasher. The main idea is that they be
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