Metal detector transmits by vibration

In addition to vibration, the detector also has a high intensity LED display which is directly in front of the diver's face and easy to see in all conditions. It’s snareless design has no external wires or cables to prevent it becoming entangled, while its and bright yellow search coil helps the operator find any target in zero visibility water.

An example: Recently, a woman lost her ring in about 3 to 4 metres of water while on a swim raft at Woodruff, Wisconsin. The bottom was a metre of weeds with silty muck on the bottom. She recruited local company Timber Bay Sports to help find her irreplaceable ring and they located 23 small targets before discovering the ring, all in just under an hour.  

www.JWFishers.com

Metal detector’s 136 year history

The first metal detector was invented on July 2, 1881 after U.S. President James Garfield was shot in the back. While he survived the assassination attempt temporarily, the problem was his doctors could not locate the bullet.  
Alexander Graham Bell, then 34 years old, learned of this and set out to build a device that could detect it. Though his machine worked properly, Bell deemed it a failure because it was unable to locate the bullet and the untimely death of President Garfield resulted.  

What Bell didn’t know was that the President’s mattress was filled with metal springs that interfered with the magnetic field surrounding the search area.
Bell’s detector was a precursor to modern metal detectors, an example of which are those manufactured by JW Fishers Mfg.

Some of those using Fishers detectors are the US Navy’s Mobile Diving and Salvage Unit, the, the US Coast Guard, US Border Patrol, Colorado Springs Fire Department, Detroit Police Underwater Recovery Unit, the Houston Police Dive Team, New York State Police, National Police Dive Squad in New Zealand, the Swedish Coast Guard, Japan’s National Police Agency, and the Royal Canadian Mounted Police.