Communication under the water is difficult compared to being in air. The Professional diver may have the need to pass critical or detailed information to his fellow diver or to topside.
As a professional diver, we need to be fluent in the various methods of underwater communications. Following are the most common techniques.
Divers have been using hand signals since the first humans explored underwater. Now we have hand signals that reflect the information we need to pass back and forth to each other. These signals are pretty well universally accepted but it's always good practice to review signals with your dive partner before you dive.
LINE PULL SIGNALS
There are certain circumstances that require the dive team to use a lifeline. A lifeline allows a single diver to be in the water provided the line is tended and a safety diver is ready to go on the surface. The lifeline can also be a very important communication tool between the diver and the surface.
It is essential that the diver and tender know some basic one pull signals. There are many different line signals. There are many different line signals that vary from industry to industry, but most line pull signals in North America are based on the US Navy line pull signals.
VOICE COMMS - Wireless Comms
One method we can have voice communications diver to diver or diver to surface is by using wireless communications. There are a few manufacturers that make and sell such communication sets and they all function in a similar way.
First of all, we need to be able to move our lips and tongue to speak and for even clear comms, we need our noses involved. To this end we generally have to use some sort of full or half face mask that enclose our mouth and nose (oral-nasal mask). There are many brands and styles in the market and there are manufacturers that make the microphone speaker assemblies for them.
The wireless comms unit consists of a microphone and earphone assembly and a transceiver module. The microphone picks up our voice and sends the signal to the transducer module.
A computer chip in the transceiver takes the voice signal and boosts it to an ultra high sound frequency which it radiates out in all directions.
HARD WIRE COMMS
Although commonly used in surface supplied diving, hard wire comms are also used by Scuba Divers on occasion. By the name, hardwire comms require a communications cable between the diver and topside. the comm wire is attached to a connector on the divers hat or full face mask and to a comm box at the surface. Hard wire comms have the advantage of being extremely reliable in most conditions.
Hardwire Comms are extremely useful when lots of detailed information must be sent to the surface, for narration of video, or when the divers voice must be recorded for an inspection report.
Although hardwire comms are clearer and more reliable, the dive team must still use proper radio operating techniques and radio talk.
DIVER RECALL SYSTEMS
For commercial Scuba operations, some form of communication tool is required to recall divers in the case of an emergency or change to the operation.
Diver recall systems generally fall into three categories, percussion, explosive, or electronic.
Percussion - There are no commercially made percussion diver recall systems, most all are home-made. These systems consist of metal pipes, metal rings or bells which are suspended in the water and struck with another piece of metal (hammer). These units are usually rather crude and are only marginally effective. Although sound is transmitted well through the water, these diver recall systems do not travel far and sometimes the sound is confused with other natural sounds so the diver misses the signal.
Explosive - There is no mistaking the sound of an explosive diver recall device. For the diver it is a very persuasive signal. On the other hand this signal device can be extremely dangerous to the diver. Explosive diver recalls are available from pyrotechnic companies but may require special permits, shipping and handling to obtain. If using these devices, be sure to set them off a good distance from the divers to minimize shock wave. Be advised that these shockwaves can wreak havoc on a divers air spaces and use of such equipment could be major liability concern.
Electronic- The safest and most effective (and most expensive) diver recall systems are of the electronic variety. Companies like Lubell, OTS and Equinox all make similar diver recall systems These systems consist of an Underwater speaker and topside control box and operate from a 12v battery. These units have an effective range of 2000 meters and can transmit recall sounds such as siren wails and yelps and even voice. These units are the most effective and safest for the diver.
Any company employing Occupational SCUBA Divers is required to have some form of diver recall system ands as a supervisor, tender or standby, you must consider how you will recall your divers.