NAUI Master Scuba Diver 244 Diving Techniques and Deeper Diving weights are secured to the float with a separate 4.6 m (15 ft) line. The entire unit is pushed to the dive site by a diver swimming on the surface. The bottom weight is then lowered and the line is made taut to the surface float. Once the descent-ascent line system is secure, the emergency air supply system is lowered to a depth of 4.6 m (15 ft). Advanced deep divers configure their diving equipment and plan their dive so that all necessary breathing gas, including emergency gas, is carried by the diver. The diver will designate 20 to 33% as emergency gas. The scuba will have a dual manifold with redundant regulators and isolation capability. Deployment Ideally, the station will be positioned by a surface swimmer prior to the dive team(s) entry. Buddy teams will enter the water quickly and proceed to the descent line. If the dive support station is used and not previously positioned, the first team will position the station. If the conditions are satisfactory, more than one buddy team may descend concurrently. If visibility is poor or surface conditions rough, two person buddy teams may deploy in a staggered fashion in order to avoid confusion and crowding during entry and descent. Descent and Buoyancy Control Once the divers are on the descent line, they should begin descent immediately, especially if there is wave activity or current at the surface. They should hold on to the line and descend feet first. The feet-first position is much better for equalizing pressure, establishing orientation, maintaining control, and reducing diver stress. One hand remains on the line and the other is used for buoyancy unit operation and equalization. Conditions permitting, most divers will pause briefly at 5 to 10 m (15 to 33 ft) to do a quick buddy check and verify equipment operation/security. Descent can be controlled by holding the descent line in one hand, locking it in the arm at the elbow, or wrapping the lower leg around it. Buddies should remain together throughout descent, ideally, facing each other on opposite sides of the line. Slow the descent upon approaching the bottom and adjust to neutral buoyancy. If the bottom is silty, avoid contacting it. On the Bottom Approach the bottom cautiously and do not stir up the silt. If the boat’s anchor line is used for descent, the first team should check and, if necessary, reposition the anchor. If operating from a large vessel, a crew member will often check and secure the anchor. If the visibility is poor, you may have to use a reel to assure return to the ascent line. It is especially important to maintain visual or physical buddy contact throughout the dive. In limited visibility, stay within touching distance or use a buddy line. Stay well above silty bottoms, maintain neutral buoyancy, and avoid kicking in a position that allows your fins to fan the bottom. If you become separated on a deep dive, it may be difficult or dangerous to surface, reunite, and continue the dive. The dive may well be over. Use natural features or an object such as a shipwreck to maintain orientation, or use a reel. Relying on compass navigation to return to your ascent line in limited visibility is generally unwise. If the water is clear, you have more navigational latitude. Establish a relaxed breathing pattern and avoid exertion if at all possible. If you overexert yourself or become “stressed” at depth, your air supply can be consumed quite rapidly. Furthermore, some regulators, especially ones in a poor state of repair, may exhibit breathing resistance under high breathing demand at depth as cylinder pressure is reduced. This can give the impression of air supply depletion. If your breathing becomes hard or heavy; stop, check your cylinder pressure, and relax. If you cannot bring your breathing under control, signal your buddy that you wish to ascend and terminate the dive. Cylinder pressure must be monitored throughout the dive. Keep in mind that you will consume approximately twice as much air per minute at 30 m (100 ft) as at 9 m (30 ft). The same air supply will last only half as long and the frequency of pressure gauge monitoring must be increased accordingly, especially near the end of the dive. Thus, the diver with the highest air consumption rate controls the dive length. Some dive
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