Monday, February 3, 2014

Police Dive Teams - How to Find People and Evidence Under Water: Information for Writers


Oxygen toxicity occurs when the lungs take in ...
 (Photo credit: Wikipedia)
Last fall at the Writers' Police Academy, I attended a seminar in how the police dives for evidence and conducts searches for bodies that are underwater.

The divers that we interviewed were all police officers; they trained on a regular basis as a water recovery team. When a need arose, they would leave their normal workday duties and dive.

These divers were involved in cases that included:
* Evidence recovery
* Submerged body recovery, including:
   `victims of a crime

Teams might also participate in:
* Inspecting the hulls of ships in
   anti-narcotics operations
* Explosive Ordnance Disposal (bombs)
   in anti-terrorism efforts

The team that I interviewed maintained a minimum of three dive members per event.
* A below water surface diver
* An attendant diver who stayed on the surface to assist the underwater diver and to signal/communicate
* A supervisor who works on the surface to direct the operation

Video Quick Study (6:05) Norfolk, England but this is the same information that we received.

Most of the diving investigations are done in highly hazardous environments which might include
* Cold temperatures
* Zero visbility
* Contaminated waters including chemical hazards
* Sharp objects that the divers must feel with their hands since they can not see
* Entanglement and entrapment objects such as submerged trees, rocks, and debris

Video Quick Study (3:32) What it looks like under there.
Video Quick Study (8:21) Difficulties of suiting up, moving, and seeing underwater.

This is picture of one of our instructors, "Cookie." Cookie's technique for keeping the heebie-jeebies at bay while he's groping through pitch-black water for a dead body includes singing as loudly as he can. That's why he makes extra bubbles.

Video Quick Study (3:34) includes information on equipment, sonar, finding a car

US Navy 090628-N-5710P-319 A U.S. Navy diver c...
 A U.S. Navy diver conducts a dive supporting Infinite Response 09, a bilateral exercise between the U.S. Navy and the naval forces of a Middle Eastern country (Photo credit: Wikipedia)
The team might be called to investigate:
* Natural water ways such as oceans, rivers,
   and ponds
* Dams
* Caves
* Sewage ponds - there's a nasty plot twist for

In some cases sonar is used to reduce diver exposure. This includes side-scan sonar and radial sonar. The sonar can help locate:
* Vessels
* Vehicles
* Planes
* Bodies
* Evidence

Search Patterns:

graphic from Wikipedia

Arc Search

* Also known as a pendulum search and a fishtail search
* The diver has a rope that is fed to him by his attendant diver.
* The diver will start on one side of a designated line (such as a shore
    line) and swim/grope through the water at the far reach of the line.
* At the end of the arc, the diver turns to go back the other way. The
   line is then released at a measured increment, knotted to maintain
   a record, and fed to the diver. For example: if the diver is looking for
   a bicycle the attendant might release a foot and a half of slack between
   arc rotations. If it is a gun, the arcs are much tighter.
* Once the diver has searched the area that can be conveniently reached
   with the rope line, the center point is moved to search another area. 
* This search works best when the general area is known.

graphic from Wikipedia

Circular Search

If the team was out in the water, away from a shore line, they would use a circular grid pattern.

This operates in a similar way as the arc search.
* Fixed central point
* Diver swims 360 degrees before his line is 

Other Search Patterns

* Jackstay - Has divers swimming a straight line along a shore then moving out a length to swim another
   straight line.
* Snagline - When an object is large enough, like a car or fridge, a line can be held in parallel swimmers'
   hands so that it will catch on the item.

English: An Engineer-Diver with KB Bandmask
 (Photo credit: Wikipedia)

Underwater communication 

Can take place via
* Line signals 
* Communicators

Once an Object is found

* The diver sends up a signal marker
* The GPS coordinates are documented
* The item is elevated using air balloons

Video Quick Study (2:21) You can see the lift bags bringing up a car.

A Body 

* Does not lay flat on the floor of the water. The upper half is held at an angle buoyed by air trapped in the
* Will float after about seven days as the body fills with gases
* After several more days as cavities are punctured by fish, birds, and other animals, the body will sink back
   into the water.
* The rate of decomposition depends mostly on water temperatures. The colder the water, the longer the
   body will remain intact.
* The deceased is bagged underwater.
   `This is for the sake of the survivors watching from shore
   `This helps to maintain any evidence that will help investigators

Video Quick Study (2:26) Divers talk about their experience and shows arc, and signalling.
Video Quick Study (3:29) Canadian and American divers certify in ice diving. YIPES! 

Video LONG Study (47:00) If you are writing a SCUBA scene you may want to spend the time learning 
                                about the problems of hypothermia, dry suit, and choices.

Thank you so much for stopping by. And thank you for your support. When you buy my books, you make it possible for me to continue to bring you helpful articles and keep ThrillWriting free and accessible to all.

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  1. Great post Fiona!
    Your blog is a must-share for anyone thinking of writing in the crime/mystery/thriller genres. Such great info.

    You noted that: A body will float after about seven days as the body fills with gases -- From this, I gather that it sinks immediately to the bottom and slowly makes it way back up after 7 days.

    My question is:

    Is it possible that a dead body in the ocean , which is particularly buoyant, will remain floating/visible after 10-12 hours PRIOR to sinking? My book is fiction and I only need the plausibility of this, even if it's improbable this would be the case.

    Thank you!

    1. Okay - I'm going to take a stab at this :)

      * Bodies sink when they are denser than water.
      * The human body is about the same density as water. When the lungs deflate then a body is denser than water and sinks.
      * Salt adds to the density of water. That's why it takes less effort to stay afloat in the salt water bodies like oceans.
      * Anything that you can write to help your corpse be buoyant would help this scenario. Ex. the person died PRIOR to going in the water
      (air still in lungs), and the body was face down, thereby trapping the air in the lungs. But you'd have to have the body go in flat.
      * Another thing that would help the body stay afloat is fat. Muscle is denser than fat, fat is less dense than water. The fatter the person the more
      * Take off their clothes (as much as is practical) a wool coat for example would become an anchor when saturated.
      * And finally, the colder the water the denser it is thereby giving the body a slight increase in buoyancy.

      Hope this helps,

      ~ Fiona

    2. I love all the pointers, Fiona, and very helpful. It will be tricky, but I think I can make it a plausible scenario. SO appreciate the help on this. xo

  2. Very informative! I missed so much of this at last year's WPA, since I was in the water. :)

    Quick question -- did you learn about the training involved to be on the special team, such as the initial training (e.g. is it all hands-on or is there an initial classroom-type training to begin, and if so, how long would that be) followed by on-going (e.g. weekend/month) training exercises?

    Thank you!

  3. Hi Rebecca,

    The answer to your question is it varies. It really depends on location/need, budget, individual experience prior to signing on, etc.

    Thanks for stopping by, was there anything you wanted to add from your experience applying the process?


  4. I noticed in the Frogwoman's video that she wore boots instead of flippers. Is that the norm? In my new novel (WIP) six bodies are weighted to a pond floor by their feet. The recovery is done on the down low because of something I can't share here. Two divers agree to find and recover the bodies from this murky pond. Would they were flippers or boots? Would they still bag the bodies underwater? And would their video be enough to document for court?

  5. Hi Sue,

    The use of fins and boots are situational. The boots are weighted and used in water with fast currents like a river. If it is in a pond or still water they would fin. Your divers would fin. Unless the torso of the body is weighted, it will float up and the divers are feeling around about a foot off the bed of the pond.

    They will bag underwater. As the bodies decay, so the ligaments and tissue that holds them together degrades. If the bodies are not bagged in situ, they can lose some of the body parts and they will float away/may be difficult to recover again, or they could lose a clue that was with the body.

    The video would be a single piece of evidence that could be brought to court. Why this isn't your beat all end all evidence: Evidence must be handled properly along a certain line of sanctioned steps. If your divers were working outside of the norm then when they are on the stand defense can rip them apart. Anything that strays from normal protocol throws the validity of the evidence into question. They would be asked about motivation and personality - do they often go off on their own and do maverick things? Would they, for example, create this evidence? And remember, a trial is a complex dance with lots of moving parts. So I'm not able to answer your question completely, but I will say - this video evidence is tainted. Hope this helps.



  6. Great post. I'm going to WPA this year and hope to take the scuba section. I am a rabid scuba diver and my new series features a scuba diver. Thanks Fiona.

    1. Thank you kindly. I'll be at WPA as well. I hope we get to meet. Stacy Allen will be there, too - looks like you have a lot in common with her. Her book Expedition Indigo will be released this month. It's a scuba diving suspense. You can read about her here:



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