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Showing posts with label police SCUBA diving. Show all posts
Showing posts with label police SCUBA diving. Show all posts

Monday, February 3, 2014

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


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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:
   `accidents
   `suicide
   `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
   you










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 
   lengthened








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
   body. 
* 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.


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