Aquatic search and rescue

CarolinaFireJournal -

07/15/2014 -

Incidence of drowning’s are not frequent, however they are often a dramatic event in a community. Local resources respond and operate to the best of their abilities until recovery is made. Recovery may be a matter of hours, days, perhaps months in some circumstances.


I aim to offer guidance towards structuring an aquatic search in the following information. Ideally this framework can easily be employed to develop an effective search using the right assets at the right time.

We’ll begin with the drowning process and human decomposition.

The Drowning Process and Human Decomposition
“Drowning is the process of experiencing respiratory impairment from submersion in liquid.” — International Life Saving Federation.This has become a uniform definition, assisting in diagnosis, registration of cause of death and research.

Contrary to popular opinion, drowning is usually silent and rapid. The classic picture of a victim yelling and thrashing in the water typically doesn’t occur.

The human body’s density and specific gravity is slightly more than that of fresh water. Thus, a body will sink to the bottom unless acted upon by some external influence.

Generally a body will sink at an average rate of two feet per second (one and one-half feet in salt water, two and one-half feet in fresh water), landing in the general area of submergence. During the body’s descent, it will move horizontally no more than one foot for every foot of vertical distance. Usually bodies won’t move once on the bottom unless affected by a current until decomposition gases cause buoyancy. Bodies tend to resist movement in current less than one and one-half miles per hour. If a diver can swim against current, usually a body will not be moved.

Typically a body will be found in non-moving water within a circle whose radius is equal to the depth of the water from point of submergence.

Always Begin the Search at Point Last Seen (PLS) or Last Known Point (LKP)

It is difficult to create specific rules for decomposition and floating. When cells stop receiving oxygen, an anaerobic process commences that produces acids. This is known as autolysis, or self-digestion. This production of acid begins to destroy the body cells. Anaerobic micro-organisms produce gases that force fluids from internal organs and destroy more cells. This process produces more gases, making the body more buoyant.

Time from submergence to floating varies. There is no definitive calculation that accurately predicts flotation. Boyle’s Law gas/pressure relationship prevents a body from suspending in a thermocline.

Planning for Response

It’s imperative for agencies that are responsible for aquatic searches to prepare for a response. Following are actions that should take place prior to an incident:

  1. Review previous incidents to determine what can be improved.
  2. Examine likely incident sites for hazards and problems.
  3. Develop written resource plans that may be needed for response.
  4. Train with all potential resources frequently.

Search is an Emergency
At the beginning of a search there are many unknowns. A person’s life may be in jeopardy. Thus, the initial response should be urgent.

The PLS or LKP is critical to searching; the more precise, the better. Often information received is vague, perhaps unreliable. Investigation is crucial in these circumstances. The accuracy of the PLS or LKP is obviously important. The effective use of resources is incumbent upon that. The PLS or LKP becomes the Initial Planning Point (IPP).

The initial response actions must be to:

  1. Investigate.
  2. Determine an accurate PLS or LKP.
  3. Define and confine the search area.
  4. Begin a hasty search of the high probability area(s).

Using Topography and Weather Conditions to Aid Search Definition and Planning
Topography and weather conditions may be useful in defining the search area. Consider areas that may accumulate and “trap” scent such as coves surrounded by trees or rock walls of a quarry, etc.

Nautical charts are useful to determine current direction and other physical properties that may affect the search.

As the search is defined, efficiency and thoroughness are critical. Consider asking for resources that will allow these two critical tasks to be performed well.

A clue is defined as a signal or message, whose information serves to reduce uncertainty regarding the missing person’s location. Clue seeking is an activity maintained by all searchers, from interviewers to patrol boats. Clues are simply waiting to be discovered.

An initial strategy is to confine the search to pertinent and significant areas, reducing it to the smallest area possible. Likely this is where the most clues are found. A search without a victim is useless.

Establishing the Search Area

The first step is to identify areas that should receive high priority. Two components will help determine that area:

  1. Determine Last Known Point, Point Last Seen, and Last Known Activity.
  2. Consider how far the person might have traveled using:
  • Water currents, especially upper and lower level determined by ‘set and drift’
  • Buoys or environmentally friendly “dye packs”
  • Wind speed and direction which is important if the victim may have floated
  • Underwater topography
  • Victim ability and survivability
  • Physical barriers such as dams and strainers
  • Witness statements

Combining these two pieces of information will assist to establish a better defined search area. Always begin a search at the PLS or LKP.

Side-Scan Sonar and Echo Sounding Search Resources
It is imperative that searchers be acquainted with specialized resources that may be of great assistance to them. Advantages for resources include, but not limited to: reducing submersion time by locating the victim, increasing searcher safety and searching large areas quickly.

Side-Scan Sonar
Dating to the 1920s an extremely useful tool for searching is the side-scan sonar. In fact, it is a critical technology that should be used for searching based on its advantages. Side scan sonar units are the best tool to create images of the sub-bottom floor and objects. Search managers should request this resource almost immediately upon commencing the search. Major advantages of sonar are the amount of area covered quickly and image resolution. Also, sonar enhances other recovery means.

Visual images provide an operator with data to analyze. This data may contain anomalies for further evaluation. Image interpretation is important, and the operator should be able to recognize sizes and surfaces. The primary purpose of side-scan sonar is a viewing tool, able to search large areas.

The echo-sounder is a technology that provides a profile of the subsurface floor. Profiling is a process of selecting echo returns for plotting. The primary purpose of an echo-sounder, or profiler, is a measuring tool. It is useful when utilized with side-scan sonar. Simply, an anomaly may be seen on sonar and confirmed by echo-sounder as to a shape and size that needs further evaluation.

K9 Search Resources and Suggestions

The following information is supplied by Roxye Marshall, N.C. Marine TF5.

A very useful search asset is the K9/handler unit. They can help define and confine a search area.

Scent/odor is the search dog’s main tool needed to perform. Searchers should understand how the K9 works and be familiar with scent/odor dynamics.

A body in water produces scent/odor, which mixes with water and is moved by currents. The scent/odor eventually reaches the surface and is moved by air currents. The scent/odor may become “trapped” by vegetation or other features on land. It is important that searchers identify “scent or odor traps.” Topo maps are a useful resource to identify these areas. Use scent/odor traps as an advantage when deploying K9 units.

Decomposition gases mix with humidity enhancing the quality of scent/odor. Water can and does enhance the scent/odor. Thus a good time to deploy K9 units is early in the morning, after humidity recovery overnight. Usually the wind speed is lower in the early morning also. The scent/odor molecules are closer to the water’s surface at that time.

Prior to an aquatic search, it is important to develop a list of K9 search resources, and how they may be summoned 24/7/365. Their abilities, certifications, and experience will be useful information when considering them as a resource to contact. At time of need isn’t appropriate to foster a relationship between K9 units and searchers. It is critical that frequent training be conducted integrating the K9 unit into such sessions. Handlers may provide useful information such as boat type preferred, crew configuration, etc.

Grappling and Dragging Operations
The age old method of “dragging” remains in use today. It dates back many years when it was the only method to recover sailors overboard. Still in use today, it remains a valid method of recovery.

Usually the actual “drag” is constructed of steel forming a framework. To the frame large treble hooks (5/0-9/0 size) are attached.

Dragging is done slowly and methodically, using parallel courses. Courses should be navigated to ensure the best coverage of an area. Coxswains should be able to guide the boat steadily and on course.

As with any search, it is very important to document the area covered. A GPS becomes very useful. Coordinates are radioed to a communications point and a map is marked to show the area searched. Also, buoys can be deployed to indicate searched areas. Along with GPS this serves as an accurate indicator of searched areas.

Interacting with Survivors and Friends

This interaction is terribly important and demonstrates professionalism with compassion. Consider the following actions:

  1. Assign a liaison to survivors/friends early in the incident.
  2. Be honest during conversations. State only the facts. Don’t enter into conjecture.
  3. Inform survivors of the search techniques used and results frequently.
  4. Exclude survivors from the “hot zone.” Provide shelter and food for them.

Boat Operations

  1. All boats used must meet U.S. Coast Guard regulations.
  2. All boat personnel must wear a USCG approved PFD.
  3. A Type IV throwable flotation device is needed on each boat.
  4. Each boat must have a rescue rope throw bag.
  5. Equipment needed for each boat:
    • First aid kit
    • Fire extinguisher
    • GPS with WAAS capability
    • Compass with adjustable declination
    • Whistle (pealess and non-metallic)
    • Map of assigned search area in protective material
    • Pencil, pen, grease marker
    • Water resistant flashlight with spare batteries
    • Two way radio and/ or cellphone (two separate means of communication)
    • Slip joint pliers
    • Assorted screwdrivers
    • Knife
    • Duct tape and electrical tape
    • Oars/paddles
    • Spare spark plug and wrench
    • Spare starter cord
    • Spare shear pin for prop
    • Spare prop
    • Anchor and line
    • Assorted zipties
    • Utility rope
    • Spare fuel
    • Spare boat keys
    • Buoys
    • Bilge pump
  6. 6. A “Man Overboard” Plan Must be Developed and Discussed Each Time the Boat Departs Land

Segmenting and Allocating Resources
The search area should be segmented. These segments can be defined by using maps and GPS. Floating buoys can be used as segment markers. High priority areas should be searched first. Outer limits of the search area can be determined by GPS coordinates and marked on a map. Specific areas, such as eddies and strainers, that are searched can also be marked on a map.

There are many bodies of water that may require searching. Rivers, flooded areas, ponds and lakes are examples. Different bodies of water will require various search strategies and tactics.

Information When Requesting Resources
Requesting additional search resources promptly is a sign of effective management. It provides the best resources to be used at the correct time, allowing the most efficient search possible. When requesting resources prepare to provide:

  • When they are needed?
  • Where they should respond to? Be specific!
  • Telephone number(s) for Command Post
  • Description of situation
  • Any special skills or equipment needed?
  • Who else is responding?
  • Predicted weather conditions
  • Current road conditions
  • Route of best access
  • Communication frequencies on scene?
  • Map resources that may be needed
  • Check-in point and information
  • How long will resources be needed?
  • What are the cancellation procedures?

Suspending the Search
Not all searches end successfully in a short time. The difficult decision of suspending the search is sometimes required. What are some reasons the victim isn’t found:

  1. The victim is outside the search perimeter, perhaps a remote area.
  2. The area isn’t searched effectively and thoroughly. Perhaps the victim is floating and obscured by low hanging vegetation.
  3. There isn’t a victim, simply a bogus search.
  4. The victim surfaced unseen and sank again.
  5. The victim is trapped by some obstruction/encumbrance.
  6. The victim surfaced unseen, was struck by a boat and sank again.
  7. The victim is caught in a strainer.

Considering the intent is to find the victim immediately, request specialized resources early in the search!

What should be considered when deciding to suspend a search:

  1. An assessment of the efficiency of search methods.
    - Have areas been re-searched?
    - Have specialized resources been utilized?
  2. A concern for responder safety.
    - Is the safety of responders compromised?
  3. A consideration for survivors.
    - Nothing is worse than the unknown

Little formal educational information is combined into a curriculum. This often translates into less efficient and effective responses. Assets are used at the wrong time resulting in additional man-hours, more expense, and prolonged submergence of the victim. Searcher safety is minimized, as they are “on-water” for extended periods. Survivors become secondary victims, suffering for a longer time.

Detection Resources for Aquatic Searches
Clue Finders
Subject Finders
K9 and Handler
Hasty Teams Divers
Grappling/Dragging Teams
Patrol Boats
Side-Scan Sonar
Echo Sounder
Thermal Imaging Cameras
Night Vision Gear
Underwater Camera

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Issue 34.1 | Summer 2019

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