Chapter 9- Search and Light Salvage Search and Light Salvage 221 ing kick cycles, by swimming for a measured time, or by counting arm spans when visibility is limited. A kick cycle is defined as one complete kick of both legs and is usually counted when one leg reaches the top of the kicking motion. Kick cycles can be calibrated by swimming along a measured length of line and counting the number of full kick cycles required to cover the distance. For example, if 25 kick cycles are used to cover a distance of 30 m (100 ft), then each kick cycle covers a distance of 1.2 m (4 ft). Alternatively, one can measure the time it takes to swim a known distance along a line to get an idea of distance covered over time. Skill in the areas of navigation and distance measuring are prerequisites for underwater searching. When swimming any line-controlled pattern such as the semicircular and circular search, it is necessary to maintain the line taut at all times. That means that the diver controlling the line will place a slight strain on the line and may even have to angle their body to maintain this strain. It is recommended that these patterns not be attempted with line that is longer than 15 m (50 ft), because the effectiveness of the pattern depends upon maintaining a taut line. A sagging or slack line causes an erratic pattern. Unlike public safety dive teams who often deploy single tethered divers, recreational divers work as buddy teams. On semicircular, circular, and other taut-line arc searches, the inside diver (diver closest to the pivot point) controls line distance and helps maintain tautness. The buddy swims on the outside of the arc, handles the reel, and maintains a fixed distance from the inside diver. The Contour Search When the probable depth and approximate location of an object lost offshore are known, a contour search can be very effective (figure 9-1). The contour of the bottom along a shoreline is followed at a constant depth. This method is not a true “pattern,” but rather a search technique. The search is initiated about 30 m (100 ft) down the shore from the estimated location and at a depth slightly greater than the estimated depth. You follow the contour of the bottom, i.e., maintain a constant depth, until you are about 30 m (100 ft) up the shore FIGURE 9-2. PARALLEL SEARCH PATTERN. from the estimated location. You then turn at a right angle toward shore to a shallower depth. The distance you move toward shore and the new depth will be determined by the visibility. You then turn parallel to shore again at the new depth and parallel your first course in the reverse direction. The distance between sweeps will be determined by the visibility and the size of the object. With low visibility or small objects the distance between sweeps will be small. Successive sweeps at shallower depths are conducted until you find the object or conclude it is not in the area being searched. Compass-Controlled Patterns Fairly precise patterns may be maintained using a compass and counting kicks. Both parallel and box patterns may be used. Such patterns are especially useful when searching for medium to large sized objects in moderate to good visibility. The parallel search is conducted by swimming on a fixed compass heading for a given distance (figure 9-2). Distance is maintained by counting kick cycles or time. At the end of the swim line, the divers turn 90° to the line of search, swim a short distance (visibility dependent), and then turn 90° to parallel the previous line on a reciprocal compass heading. This procedure is repeated numerous times and fairly large areas can be covered in a short time.
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