SEARCH TECHNIQUES FOR DIVERS
DIVE RESCUE SERIES
There is no perfect search and rescue system. As rivers, streams, lakes, ponds, and quarries differ, so will the search techniques necessary for a successful find. Choosing the appropriate technique for a situation depends on a number of factors such as physical site, water depth, water speed, bottom contour, object of the search, and amount of area to be covered.
Let’s examine some commonly used search techniques. Bear in mind that the techniques may have to be modified in keeping with the specific requirements of the incident, the capability of personnel, and the safety of divers. Remember, too, that adequate training is essential to safe and effective operations.
This technique involves using one bottom line approximately one inch to 1 ¼ inches in diameter and no more than 125 feet in length. A heavy weight of 15 to 25 pounds is attached to each end of this horizontal line. It must be heavy enough so that divers won’t dislodge it from the bottom during their search. Connected to each weight is a smaller vertical line 5/i6 to ½ inch in diameter with a float of 10 pounds minimum buoyancy (approximately 2to 2’/;-gallon container).
Divers descend to one end of the weighted running line. Then they slowly travel toward the other end of the running line, methodically searching as they go. When they reach the opposite end, they move the weight 2½ to 3 feet (or as visibility dictates) further upstream, attempting to take advantage of a light-moving current, in order to sweep away any disturbance their previous path causes. They then return to their first point of entry, searching as they go. Upon reaching the reverse side, they once again move the weight upstream an appropriate distance in order to search new territory on the way back. They continue this pattern until either the divers find what they’re looking for or they have exhausted bottom time.
This technique can be used with a single diver down who’s tethered back to the surface or a two-diverdown system with no tether back to the surface. It also can be used perpendicular to a light current 1/4 to 1/2 knot maximum or up current (face lines parallel to the current) with speeds of up to one knot. The jackstand system lends itself extremely well to nearly flat contour bottoms and to searching for rather small items, such as weapons, evidence, and personal property. It is usually considered to be a methodical search but hot the best one for covering a large amount of bottom acreage in a short period of time.
This technique is often used in the same type of terrain and water conditions as the standard jack-stand. It involves using two weighted running lines, both requiring their own vertical buoys attached (similar to the standard jack-stand). The divers slowly search, as dictated by the situation, until they reach their weighted end. A signal, mutually agreed on, directs each diver to let out IV2 to 2 feet of line (or as dictated by visibility) from an interdiver connection. They then move the weighted line the appropriate distance outward and slowly search their way back to the other end.
The Williams stand works extremely well across small streams and rivers, allowing shore tenders to make the appropriate moves to expand the search when the divers are in position. This system isn’t used very often since it is personnel-dependent and is too slow to cover a lot of bottom quickly.
The half moon is second in popularity to the jack-stand system. It allows a much faster bottom search than jackstand searches and covers more acreage quickly. It is extremely useful at the end of jetties or on an unsmooth beachline. It also works well when more than one team of divers is available to search a given area.
The divers are first deployed at the most remote point of the area to be searched at the end of the guide line but no farther than 150 feet—signals become extremely difficult to transmit beyond that—and work methodically back toward shore.
This technique allows the divers to start diving at the farthest distance from the support staff. They work closer and closer toward shore as they use up their air supply.
A half moon works relatively well in nonflat, contour bottom situations and extremely well in searches for large objects such as automobiles. The tender attempts to keep divers in a reasonable depth of water in order to minimize the number of equalizations (clearings of the ears). Tenders accomplish this by working the divers to a maximum of a 60-degree angle to the shore. The semifloating line is best for avoiding snags such as catching the car on the line. In most cases the one-diver-down system works well in the half moon technique, with a harnessed backup diver on shore.
This is not usually a good grass technique, since the line can become caught in the grass, causing the divers to lose their patterns. Another problem is that the enormous weight from the grass can be picked up by the line.
In this technique the divers and the tender move at direct right angles to each other. It usually dictates a twoman backup system. The diver and the tender move as one unit. The twoman backup team should split—one diver stands by at the midpoint and the other at the corner of operation in case a diver rescue is required. The pier walk allows the diver to begin searching close to the shore or the dock. It works rather well for searching large areas and when searching a long, right-angle shoreline.
A semifloating tether line made of dacron/polyester is effective in lowdebris areas and in vehicle searches. The pier walk can be used in deploying the divers in both an outward and inward motion, depending on the dive supervisor’s decision and the currents. It is mostly used broadside to a current with speeds of up to 1 ½ knots.
The pier walk technique is usually very quick and thorough. New York Fire Department dive teams have used this system with much success.
The circular search allows divers to make circular motions around the bottom while tethered to a center point. This center point can be any of the following:
- another diver sitting on the bottom, letting line out as needed for the working diver to continue to increase the size of the search;
- a swivel attached to a heavily weighted-down line off the stem of a platform, allowing divers to make free 360-degree turns as dictated and to extend the size of their search area by letting line out from a premarked spool attached to their harness; or
a heavily weighted unit on the bottom with a free-moving spool at the top, also allowing divers to make undisturbed 360-degree turns and to extend the size of their search area by letting out line on a premeasured spool attached to their harness.
Note: Divers must place a marker of approximately two pounds on the bottom so that every time they complete a 360-degree turn they will know where to begin extending their search. They must move this object with them along the bottom as visibility dictates the expansion capabilities of the pattern. Whenever there is no tether line back to the surface, use a two-man-down system.
RUNNING LINE SEARCH
The running line search is extremely useful in areas involving heavy grass or debris. Divers go straight out (normally on a hard-wire communication system) to the extent of the needed search pattern. The tender then moves two feet, maintaining a 90degree angle to the diver and bringing the diver back directly toward him. At the appropriate time, the diver is stopped and again both he and the tender move in the agreed on direction and the diver searches again. A weight can be attached to the end of the line if a communications system is not in use. This technique affords reasonable control of the diver while attempting to control the amount of grass the line snags. Such snags create enormous drag and cause the diver to lose pattern control. The technique also allows divers to crawl up and over underwater debris and to untangle themselves as they return, with a minimum loss of area searched.
Excellent buoyancy control really helps when searching grass for a body, since very often in the initial stages the grass mats and causes the body to stay relatively close to the top of the grass. Divers, while crawling through the grass, often disturb it and cause the body to sink down into the grass. Proper buoyancy control helps divers conduct a proper search just above the grass, allowing them either to visually find the victim or spot unusual depressions in the grass’s upper layers. As an experiment, try letting a diver gently lay on top of the grass the way a drowner would, and note the results.
Sleds can cover extremely large areas of terrain in a short period of time and involve dragging one or two divers beneath the surface. Sleds look like underwater toboggans, with airplane-like controls that allow for ascent and descent. They are not the most accurate types of search patterns, since the boat towing the sled may not be capable of returning to a close enough reciprocal course to have maintained minimal area search. They are, as underwater scooters, excellent for high-visibility (10to 15foot) searches of large areas. Practicing with sleds is essential: Too rapid a rise could cause hidden lung overpressurization problems. A real rescue is not the time to make your first sled search.
WORKING FROM A PLATFORM
Any time you have more than a 1to 1 ‘/2-knot current you should work from either a dock/pier or a floating platform. Remember that the divers affect the stability of the vessel or platform. If their search swings are too large, the stern of the vessel will travel in the same direction as the divers. This causes major additional fatigue as well as loss of pattern control.
Contain the divers in a smaller search area, and when the time comes to move on to new territory, move the boat slightly with dual anchors. Place each anchor at between a 45and 90-degree angle to stabilize the vessel and allow it to move right and left without disturbing the anchorage. Remember, you need additional scope due to the weight of the diver behind the vessel or your anchorage may not hold.
Whatever search method is chosen, a heavily weighted-down line at the stern of the platform may be required in order to get the divers to the bottom initially. The current will affect the ability of a tethered diver to reach the bottom in close proximity to the platform.
A second mobile vessel should be placed 100 to 110 yards downstream from where the divers are working in case they suddenly break free. (See Fire Engineering, “Moving Water,” Oct. ’86.) This technique should be practiced prior to its use.
FREE SEARCH-NO LINES
The two most common times to work with free search techniques are:
- in an extremely restricted area where debris, trees, or underwater growth would continuously hinder the movement of a tethered diver. This search technique requires a twodiver-down system (buddy diving plus redundant breathing system). It is most commonly used in confined areas where the diver cannot wander too far.
- in very fast water (3 ½ knots plus). Divers are deployed, drift across the bottom, are retrieved after surfacing by trained surface rescue personnel, and are taken back upstream to begin again. Fast water drift searching requires much practice and a highly trained surface support crew with meticulous minute by minute recordkeeping to minimize the dangers of a lost or injured diver.
Some tips for effective and safe diving:
- Diving is only as safe as the capabilities of your personnel.
- Professional training is available and every dive team—no matter what their level of expertise— should take advantage of these training opportunities.
- Public safety divers should always be outfitted with a pony bottle and an additional regulator to help protect against personal emergency. (See Fire Engineering, “Air: Most Important When It’s Not There!” July ’86.)
- Most witnesses of water-related accidents estimate the victim’s location 25 to 30 percent short of the actual distance. Take this into consideration prior to setting up for your first search of the area.
- Whenever a vehicle is discovered under water, attach a floatable buoy prior to surfacing—it helps you to find it the next time you look for it.