The reasons why people dive are as numerous and varied as divers themselves. For many, it's the simple lure of a temporary respite from the hustle and bustle of the surface world and a retreat into an alien world of solitude. One drawback to this experience, of course, is the inability to share it verbally with others around you underwater. Until very recently, underwater communication for the sport diver has consisted of little more than a series of erratic and often misunderstood hand signals.

In the past few years, technology has made giant strides in this field and recently I had an opportunity to try out the compact and futuristic-looking Dive-Link system. Designed by Mark Stone of Stone Electronics in Victoria, B.C. and now marketed by Scubapro, the Dive-Link consists of two main parts worn by the diver. The lightweight, contoured headpiece contains the transmitter, receiver and removeable, rechargeable battery pack. The NiCad battery charges fully in 14 hours, has an operating time of over four hours and emits a warning beep when power is getting low. A switch, mounted on the headpiece, turns the unit on and off and can be set to transmit a loud emergency signal. A small disc attached to the headset by a thin wire slides under the hood for bone conduction of sound. The headpiece attaches easily to your existing mask.

The second part of the unit is a rubber mouth-mask or speaking cavity, which replaces the mouthpiece on any regulator's second stage and is connected by wire to the headpiece. An optional version incorporates a connector in the wire which allows the mouth-mask to be disconnected from the headpiece and reattached, even underwater. To hold the mouthpiece securely, it is necessary to bite down on two small nylon retaining clips that protrude from the mouth-mask. At first glance, these didn't look too comfortable but after wearing the unit for a few minutes I was surprised at how comfortable it was. Speaking was easy and the unit is voice activated, leaving your hands free for other tasks.

When the emergency signal is activated, a loud beep is transmitted for eight seconds and repeated on a 16 second cycle. Verbal transmission is possible during the emergency signal and reception was possible during the silent eight seconds of the cycle. The mouth-mask is floodable and purgeable and taking it out of my mouth and replacing it while submerged was not a problem.

During a test dive our progress and conversations were monitored by a tender in a boat on the surface. The surface unit consists of a battery-powered, earphone headset with a boom microphone and an antenna transducer on the end of a 10 metre length of cable which is lowered into the water. Longer antenna transducer cable options are available. Volume can be controlled at the headset while squelch and gain are controlled automatically. The Dive-Link can sense talk versus noise and will not trigger on bubble sounds. With one person speaking at a time, diver to diver, diver to surface and surface to diver communication was possible and reception was very sharp and clear in all directions. As with any underwater communications system, slow, well enunciated speech is best. Conversations can also be patched into PA systems and audio visual systems if desired.

The antenna of both units must be submerged for the system to work and the cylindrical antenna transducer on top of the headset is designed to give 360 degree broadcast. The signal is also sent out at 90 degrees to the cylindrical axis of the antenna and because of this, divers may occasionally have to adjust their body position and direction to maintain communication. During our test dive, my buddy and I were able to communicate while well out of visual range, sometimes in excess of 30 metres apart. The spec sheet claims a maximum working distance of 300 metres and a maximum depth rating of 60 metres.

The Dive-Link is versatile. It can be attached to a full face mask or the headpiece can be used by itself as a receive-only unit, a useful tool when working with students. Overall, the Dive-Link is tough, well built, comfortable and simple to use and could be a valuable asset in many diving situations. More information is available at Scubapro dealers.