SAR SWIMMING TECHNIQUE
Quite a bit has been written concerning various techniques and methods of searching in an underwater environment. There are a myriad of search patterns that can be utilized depending on such factors as terrain, visibility, depth, the nature of the object being sought, etc. However very little has been written concerning the swimming technique that a diver should utilize when conducting an underwater search.
This is not a critical concern in clear open water where limited visibility is not a factor. In such cases a normal fining technique such as a flutter kick, or even a scissor kick, can be effectively utilized. However in those environments prone to silting, normal fining and swimming position will undoubtedly stir up silt effectively reducing what visibility may be naturally present in the water to a black water situation.
In potential silting environments it is important for the diver to stay off the bottom. Buoyancy control in this regard is critical. Over weighting is the biggest factor in buoyancy control. Ideally, a diver should wear only enough weight to remain neutral in 15-20 feet of water with an empty B/C and a near-empty cylinder (500 PSI).
Part of the solution lies in proper weighting. Excessive weight worn by a diver causes several problems:
Over weighting causes a diver to swim through the water at a very inefficient attitude. The weight belt pulls the diver’s lower body down while the air in the B/C, in order to counteract the weight, pulls the shoulders up. This exposes an excess of frontal surface of the diver and increases drag. Such an attitude makes for a very tedious search with the diver constantly fighting against the forces of gravity and buoyancy. Matters become even more complicated when the area to be searched consists of an embankment where buoyancy is constantly changing as the diver moves (in a circular fashion) throughout the search area. For this reason the “Jack-Stay” should be considered for employment in the search of an underwater embankment.
Increased air consumption from the added bulk and drag of an over- inflated B/C. If the B/C is not inflated to compensate for the extra weight, the diver’s buoyancy is significantly negative causing constant kicking to maintain position and counteract gravity, thus increased air consumption.
Becoming tired quicker from working harder than necessary due to the combined effects of carrying extra weight and fighting excess drag. Fatigue results in increased air consumption, decreased bottom time, and decreased size of the search area covered.
Increased breathing rate and nitrogen level causing potential decompression problems. Increased work causes increased and deeper breathing resulting in a greater absorption of nitrogen.
In order to stay clear of the bottom, it is necessary to maintain slightly positive buoyancy. In order to stay in position, it is then necessary to dive in a head-down/feet-up position utilizing the fins to counteract this increased buoyancy. This is, needless to say, not the most efficient of swimming positions, but it is necessary to get the job done. Weight worn on the waist requires that the diver arch his back. This places tremendous strain on the back muscles, especially if a diver is over-weighed. Not only should the correct amount of weight be utilized, but it should also be efficiently trimmed. Removing some of the ballast weight from the weight belt and placing it at the level of approximately from the shoulders to the bottom of the rib cage will help to naturally achieve this in-water position.
Fining technique is the other part of the equation. A full-on flutter kick produces excessive turbulence toward the bottom and will in short order reduce visibility in a silt prone environment from inches, or even feet to zero. To avoid this problem it is suggested that an alternative fining method be utilized:
Modified Flutter Kick – this is accomplished by bending the knees slightly and shortening the kick stroke. When maintaining a head-down / feet-up position, all fin movement takes place above the center of the diver’s body thereby minimizing the movement of water below the diver.
Frog Kick – this is accomplished by spreading the legs laterally, rotating the bottom of the fins inward, and bringing the fins together. The frog kick restricts the thrust and turbulence in the water to the area to the immediate rear of the diver.
Sculling – involves a gentle, steady back and forth fin movement with the fins angled slightly. The ankles are utilized to move the fins in a kind of oval pattern. Absent any current, sculling allows the diver to hold and maintain a stationary mid-water position.
When properly weighted and trimmed and neutrally buoyant, a diver should ideally be able to adjust / control buoyancy through such subtle means as breathing control or through movement of the head by use of the planning surface of the facemask.
There are additionally other factors that contribute to diver efficiency in the water:
Speed of swimming – The effort required to increase swimming speed is disproportionate to the result achieved. Doubling the swimming speed of a diver takes four times the output of energy. As discussed above, as increased energy is utilized (work is increased) so also is increased air utilized. The movements of a SAR diver underwater should be slow and methodical. Slow, short fin strokes are more efficient than rapid or wide strokes.
The streamlining (trim) of equipment – Consoles, octopus regulators, lights, etc. left hanging loosely from a diver contribute to drag as well as subject the diver to possible entanglement. All equipment should be secured by snaps, etc. or stored in pockets or pouches to make the diver and gear as streamlined as possible.
Adequate exposure protection – Thermal protection appropriate to the diving environment should be worn. A warm, comfortable diver will operate much more efficiently.
Proper breathing – Breathing affects underwater efficiency from both an air consumption and a buoyancy aspect. Breathing should be slow, and deep. Full, slow inhalations followed by a pause, and full, slow exhalations will make the most efficient use of the air supply, deliver the best supply of oxygen to the lungs, as well as off-gas carbon dioxide.
Physical fitness – Few SAR divers are employed in the diving industry (diving instructors, commercial divers, etc.) and it is difficult with all of the other demands of life (work, family, finances, etc.) to do enough diving to remain physically fit and capable for SAR operations. Obviously the best exercise to keep in shape for diving is diving itself. However, other aerobic and resistance training is of benefit: swimming, running, weight lifting, racquet ball, hiking, etc. etc. all contribute to an overall level of fitness which will serve to improve diving efficiency.
Mental attitude – A diver whose “head is not in the game”, who is preoccupied by work, family, financial, etc. problems or a diver who is stressed by or apprehensive about the nature of an operation or assignment or is worried about some equipment problem or mal-function, will operate inefficiently.