Underwater Rescue Equipment-Diver Safety Sonar

The safest place for a diver is above the surface. Using scanning sonar before a diver dives can identify potential hazards and provide critical information for effective dive planning. An effective method of guiding divers with scanning sonar is the use of surface air and wiring communications.

In the lower left sonar image, anchor cables attached to the dock’s floating pontoon were discovered during the body search. Because the dive was planned in advance (and monitored in real time on the scanning sonar display), the mooring diver did not get tangled in the anchor line while swimming underwater.

MS1000 Diver Real Time Navigation Sonar System Configuration

-Computer loaded with MS 1000 software

-MS 1000 interface unit (operates at 120/240 VAC or 9-30 VDC power supply)

-Kevlar cable (recommended length is 75m-100m)

-675 kHz high-resolution scanning sonar head with fan beam transducer (or multi-frequency high-resolution sonar head) with compass option

-Tripod

-Manual controller

Diver Navigation

Scanning sonar remains an appropriate tool for divers to navigate, deploy equipment and identify potential targets and hazards before the diver enters the water. Sonar operators and divers should examine sonar data and decide how to efficiently investigate potential targets. When the sonar head is firmly fixed near the bottom, accurate relative position can be obtained without the use of an underwater tracking system. In addition to detecting targets, scanning sonar can be used to track a diver’s search trail to confirm that the area has been thoroughly inspected. 

How to instruct a mooring diver who communicates with the surface while navigating underwater is very simple. All directions are given when the diver is facing the umbilical. The mission is more efficient if the dive supervisor can hear cues from the sonar operator. Supervisors should give tighter control of umbilicals compared to commercial diving operations, notify the dive supervisor when the diver moves towards or away from the umbilical to release the appropriate length of umbilical. When instructing the diver to move left or right, the supervisor must secure the umbilical so that the diver can use it as a pendulum.

Safe diving distances from sonar transmitters

Potential health risks exist when divers work near sources of emitting sound. In addition to military planning, security issues are often mentioned. In military planning, anyone diving into the water would be concerned about the human hazard from the use of high-powered naval sonar. Therefore, in response to this issue, a special appendix the U.S. Navy Diving Manual is attached. It is recommended that this manual be archived in every sport, commercial and public safety diver’s personal library, which covers almost all diving related issues.

The U.S. Navy Diving Manual describes low-frequency and high-frequency sonar (250kHz or higher) and provides detailed instructions for divers working with diving caps and dry diving helmets. The manual lists exposure times and acceptable SPL ranges. At the time of this writing, the manual states that at a sound pressure level (SPL) sonar output of 215db, a diver wearing a diving helmet must approach no less than two yards (1.9m/6.24′) and the permissible exposure limit (PEL) must not exceed 120 minutes. When a diver uses a dry helmet, there are no restrictions on the use of high frequency sonar. If a diver experiences any discomfort due to active sonar or other sound sources, immediately suspend diving operations. The information above about safe diving distances from transmitting sonars is an overview interpretation of the U.S. Navy Diving Manual. It is the responsibility of diving contractors, public safety diving teams, diving supervisors and divers to review current regulations, regulations and standards and adhere to diving guidelines that are very close to active sonar.