NAUI Master Scuba Diver 210 Limited Visibility and Night Diving How to Find Your Way in Limited Visibility You can use several methods for insuring proper direction referencing, including: • Reel and line (be trained in and practice these skills before attempting to use them in actual low visibility conditions). • Time your trip out and follow a timed reciprocal course on the return. • Reference objects or bottom slope, reversing the sides they appear on for the return trip. Take notes on a slate if necessary. • Be aware of depth changes and current direction • Use surface light direction (if some surface light is available). • Remember that ripples on the bottom usually form parallel to shore. As has been stated previously, avoid silt on the bottom, especially in fresh water or under no-current conditions. Use of protective gloves (to avoid being cut by objects which you don’t see), as well as exposure suits is important in low visibility diving. In zero visibility conditions, one hand held well out in front of the mask may protect it from breaking in the event you accidentally run into an unseen stationary object. The other hand may be placed beneath you as you swim in a slow, neutrally buoyant, fins-off-the-bottom fashion during the dive. The dive knife should be arm or chest mounted to ensure easy access should you become inadvertently entangled in a submerged line or rope. A smaller, very sharp dive knife is recommended for use in low visibility. This will enable you to mount it on the arm or chest and thus increase your access to it in case of a low visibility line entanglement. NIGHT DIVING Many of the techniques used in limited visibility diving are applicable for diving at night. Why dive at night? For the excitement, for lobster crawling around in the open, for phosphorescence bursting off the tips of your swim fins, for the gentle stroking of giant parrot fish or sleeping sunfish, or for a once-in-a-lifetime dive with millions of mating squid. Freshwater divers often see pike, walleye, and muskies at night. Many types of eels and octopus are out swimming freely at night, whereas they usually stay hidden in crevices during the daytime. Dive at night for the fun and adventure. Night diving has a way of focusing your attention, of making the things you encounter more interesting and more colorful. Using a light source undiluted by the filtering effect of the water makes those colors more vibrant than you have ever seen them in the daytime. You will also encounter creatures you have never seen on day dives and find the timid daylight ones amazingly approachable in their nocturnal stage. FIGURE 8-3. DESCENDING ON AN ANCHOR LINE IS RECOMMENDED IN LOW VISIBILITY. FIGURE 8-4. A REEL IN LOW VISIBILITY CAN BE USED TO MARK A RETURN PATH.
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