Chapter 9- Search and Light Salvage Search and Light Salvage 223 nique is somewhat inefficient, it maintains the buddy system. Semicircular Search A variation of the circular sweep is the semicircular search, which is used from a shoreline, straight reef, pier, or jetty which form the extremes for a semicircle (figure 9-5). A line is anchored in the center of the search area and along the straight edge. The line may extend from shore or be anchored at the bottom. Searching is conducted in the same manner as the circular sweep except that one reverses direction at the end of each semicircular sweep. In addition to use from shore, a version of the semicircular search is useful when searching for objects that have fallen overboard from an anchored boat. A boat at anchor swings in an arc on the anchor, especially when there is a wind. An object falling into the water at a certain position relative to the boat will probably not be where you think it is due to the lateral movement of the vessel. A line attached to the anchor can be used to sweep back and forth in the area traversed by the boat, thereby increasing the chances for success by employing an appropriate methodical searching method. Straight Line Search Patterns Straight lines form the basis for the majority of search patterns. These patterns are very adaptable to a variety of conditions and situations. Straight line searches can be conducted in several ways: • A compass or a compass board may be used to navigate along straight lines to methodically cover an area. • A line can be strung in a straight line along the bottom and used as a reference for a straight line search, then repositioned to allow methodical searching. • A grid of rope or PVC pipe can be spread out on the bottom, to designate search areas. • A planing board or diver’s sled can be towed along a straight line course by a boat. • A number of geometric shapes can be utilized, including square, rectangular, square spiral, or jackstay. The use of a compass to conduct a search pattern is not easy. There may be no landmarks on a featureless bottom, and you may even believe you are going in the wrong direction at times. You may not be able to effectively navigate with the compass and search simultaneously. One member of a buddy team should be responsible for navigation and swimming a search pattern. The other team member should maintain buddy contact and thoroughly scan the surrounding area continuously for the object being sought. More accurate patterns can be achieved with a compass board than with a compass by itself. Pulling a diver on a planing board (sea sled) or a tow bar behind a boat is normally a procedure reserved for use when a large object, such as a wreck, is being sought and the search area is very large. There are hazards associated with the use of a planing board, such as entanglement, rapid ascents, and bumping into submerged objects. The use of a sea sled is discouraged unless you have training and supervised experience in the use of one. A grid search is useful when looking for small objects in a well-defined area. The grid is constructed of rope or of PVC pipe and is spread out on the bottom. FIGURE 9-5. SEMICIRCULAR SEARCH PATTERN.
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