NAUI Master Scuba Diver 236 Diving Techniques and Deeper Diving Environment The nature of the environment dictates both depth and personal limitations. Thousands of divers casually cruise at 30 m (100 ft) depths in clear, warm tropical waters wearing only a thin, nonrestrictive dive skin. For an experienced diver, such a dive can be exhilarating and rewarding. However, for the same diver, a dive to the deck of a sunken ship in the dark, icy waters of the Great Lakes encased in a dry suit could be extremely difficult. When planning deep dives one must consider wave conditions (producing adverse conditions at decompression or safety stop depth), current, visibility, and water temperature. If the environmental conditions are unsatisfactory or too demanding on the diver, a prudent individual will cancel the dive. Only through a progressive acquisition of environmental experiences will an individual develop the necessary skill and knowledge required to make such decisions. Diving Companion Solving a problem and safely ascending to the surface from deep depths can be extremely complicated, especially if one does not have a capable companion. First of all, when selecting a diving companion for a deep dive, or any dive, select someone who is not going to be a problem. If the diver exhibits evidence of inadequate training, lack of experience, nervousness, overconfidence (cockiness), carelessness, or other undesirable traits, find another buddy or postpone the dive. Ideally, dive with an individual you know to be properly trained, experienced, and equipped and that you have been diving with before. Equipment For dives to, but not exceeding, 40 m (130 ft); conventional recreational scuba diving equipment will generally be adequate. However, depending on the environment, dive profile, underwater task, and diver’s air consumption rate the volume of air contained in a conventional scuba cylinder may be marginal to insufficient for safe diving. Divers are encouraged to maintain 15 to 30 percent of their air supply in reserve for unexpected or increased air demands that might be associated with ascent (i.e., difficulty locating ascent line or sharing air with another diver). Divers must take into consideration that added thermal protection may be necessary at deeper depths, especially in northern waters. Wet suits compress considerably at depth, reducing thermal protection and buoyancy. Many cold water divers now use dry suits even in the summer months for deep dives. When diving from a vessel it is imperative that divers maintain orientation and return to the surface via the ascent line. Precise compass navigation may be required. Ideally, the ascent line should be clearly marked, especially if there is more than one descent line in the area (as found on some popular shipwrecks). For some locations, especially if visibility is limited, divers will use a guideline dispensed from a small reel. The guideline (tag line or distance line) is attached to the ascent line and played out as the diver moves away. Obviously, divers will need instrumentation for determining depth and dive time. The increased popularity of dive computers has greatly simplified deep diving. See chapter 5 for a complete explanation of dive computers. PLANNING A DEEP DIVE Many factors must be considered when planning to dive deep. Some things to consider include the dive site, environmental conditions, equipment selection, cylinder size and valve, regulator(s), and other equipment. Dive Site If possible, select a dive site that is protected from heavy wave activity and offers good anchorage. Many popular dive sites, especially shipwrecks, have permanent moorings placed by diving or governmental organizations. If diving from shore, select a site where the planned dive depth is readily accessible within a short swimming distance. Environmental Conditions Environmental conditions to consider include the
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