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NAUI Scuba Diver 180 Diving Environment Verify What You Have Learned Review the following questions about the physical characteristics of a site: 1. Who is best qualified to give you an orientation to a new area? ____________________________ 2. Two types of overhead environments that require special training are ___________ and _______________. 3. Two types of man-made dive sites are ____________________ and _______________________. 4. Two types of natural dive sites are ____________________ and _______________________. 5. The bottom of a dive site can be composed of _____________, _____________, or _________________. 6. The underwater environment is usually an extension of the _______________. WATER CONDITIONS Water temperature and visibility are probably the two most important factors in determining the ease and comfort of your dive. Diving in warm, clear water is relatively simple, because you must wear only a minimal amount of insulation and it is always easy to see where you are. Diving in colder, darker water is more difficult because you must wear more insulation to be comfortable and it is not always possible to tell exactly where things are under water beyond the range of your vision. VISIBILITY A major factor affecting all dives is the underwater visibility, which can range from zero to well over 30 meters (100 feet). Diving in water where the visibility is severely restricted can be hazardous, and zero-visibility diving requires special equipment, training, and procedures. FIGURE 8-10. A BUDDY LINE IS ONE WAY OF MAINTAINING CONTACT IN WATER WITH POOR VISIBILITY. If you arrive at a site and find that you cannot see anything under water, you should postpone the dive until a day when the visibility is better. Zero-visibility diving is a necessary part of search-and-recovery diving training, but it is not fun or safe when you are just learning to dive. The locale, seasons, weather, water movement, composition of the bottom, and other factors affect underwater visibility. For example, in California visibility is usually best during the calm fall months, and worst during the winter rains and storms. In the Sea of Cortez, in Mexico, there is good visibility in the summer months and poor visibility in the winter months. Tidal changes also affect visibility. See Tides on page 183 for information about tides. Several problems relate to poor visibility. The most common is disorientation. With limited visibility, you can become disoriented and dizzy from a lack of visual references while you are submerged. You can avoid this by not diving in poor visibility until you have been trained in the proper techniques. Entanglement in fishing line and other debris can also be a serious problem in low-visibility conditions. There are special techniques for diving in limited visibility. Divers can hold hands to stay together or use a buddy line (figure 8-10). A buddy line is a short length of rope up to 2 meters (6 feet) in length, with a loop at each end. Each diver in the buddy team holds one end of the line to maintain contact. Limited-visibility diving


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