Chapter 8- Diving Environment Diving Environment 181 is a specialty area. Your instructor will cover any special techniques that relate to visibility where you will be diving. In extremely clear water, estimating distances can be difficult (figure 8-11). The surface, your boat, and other things appear closer than they are. When this happens, it is easy to exceed your planned depth, because some objects will be deeper and further away than they appear, as well. Under these conditions, it is important to monitor your depth gauge even more frequently than normal. Whether visibility is good or poor, you can see why you and your buddy must stay close together under water. In poor visibility, it is easy to become separated and lose track of one another. If you are unable to find your buddy within one minute under these conditions, you must surface, using the standard technique to search for a lost buddy. In good visibility, it is easy to get too far apart, which means you will be unable to help if your dive buddy needs assistance. Begin developing good diving habits from the very first time you go under water. If you want to be considered a good buddy, learn to stay within touching distance of your buddy without getting in their way. TEMPERATURE Water temperature can range from freezing to over 30°C (86°F). Diving in water colder than about 26°C (79°F) normally requires that you wear some type of diving suit, depending on the duration of your dive, your activity level during the dive, and your individual physiology. As a rule, the colder the water, the more insulation you will need to wear. Almost all diving requires some type of insulation because the water temperature will be colder than your body’s skin temperature. Even if you usually dive in reasonably warm water, you will need to prevent getting chilled because of the water’s capacity to conduct and absorb heat, you will chill rapidly if you do not wear adequate protection. Water temperature is always a major factor to consider when planning a dive. In most cases, the deeper you dive, the colder the water temperature. In freshwater lakes, a phenomenon known as a thermocline will appear in the summertime (figure 8-12). This is a thin zone of radical change in water temperature between the warm surface and cold bottom layers. FIGURE 8-11. CORAL REEFS USUALLY HAVE EXCELLENT VISIBILITY THAT CAN BE GREATER THAN 30 METERS (100 FEET). Surface Warmer water Colder water Bottom Thermocline (Depth Varies) FIGURE 8-12. A THERMOCLINE IS A DISTINCT, THIN ZONE OF RADICAL CHANGE IN WATER TEMPERATURE BETWEEN SURFACE AND BOTTOM LAYERS OF A LAKE.
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