Diver Recall Systems

Que ce soit pour la plongée récréative, la recherche ou le travail commercial, la plongée place les humains dans un environnement fondamentalement dangereux. La visibilité, les effets de la pression et la distorsion du son limitent la communication entre les plongeurs et l’équipe en surface, rendant la coordination en temps réel difficile. Le temps de réaction est crucial en situation d’urgence, et tout retard peut être dangereux.

Les systèmes de rappel des plongeurs sont des outils de sécurité essentiels qui comblent cette lacune de communication, permettant aux équipes en surface d’alerter immédiatement les plongeurs lorsque les conditions changent ou qu’une urgence survient, nécessitant la fin de la plongée ou une autre réponse d’urgence.

Méthodes Courantes

Les équipes en surface peuvent signaler les plongeurs en frappant une gueuse (poids) de plongée, un marteau ou un tournevis contre la coque du bateau ou l’échelle. De nombreux plongeurs rapportent qu’il leur faut un certain temps pour reconnaître le rappel, même lorsqu’ils s’y attendent.

Surface marker buoy (SMB) tags consist of a carabiner or bolt snap sent down a diver’s line with a note or mini slate attached. Divers feel the tag hit their spool or reel and read the attached message that explains the situation. This method requires a diver to have an SMB deployed and the surface operator to reach the SMB and manipulate the line.

Revving a boat engine is widely considered unreliable and inconsistent as a signal. Divers often can’t distinguish it from normal boat noise, especially during deeper dives or in areas with heavy marine traffic.

An underwater speaker attached to a cable dangles in the water at an optimized depth to transmit signals from the surface to divers underwater. © Courtesy Oceanears

Pyrotechnie

Un système pyrotechnique de rappel des plongeurs, souvent appelé thunder flash, est un outil spécialisé utilisant des détonations sous-marines contrôlées pour envoyer des signaux forts et indiscutables aux plongeurs. Lorsqu’un thunder flash explose sous l’eau, il génère une onde de choc intense dans toutes les directions. Le son et l’onde de pression qui en résultent se déplacent efficacement dans l’eau, et les plongeurs rapportent entendre et sentir la détonation sur plusieurs dizaines de mètres.

Some are ignited at the surface and then dropped over the side; others are hydrostatically operated and go off once reaching a specific depth. Each type has a disadvantage depending on your dive environment — you may be shallower than a hydrostatic device’s minimum operating depth or have an ignition flame that can injure the operator and spell disaster near oxygen tanks or fuel canisters.

Thunder flashes are no longer common in the dive industry due to several factors. Recreational dive operations avoid them for liability reasons, as they can cause hearing damage, barotrauma, and significant disorientation. Environmentally conscious divers don’t like throwing disposable and nonrecoverable units in the water.

While not suitable for every dive operation, pyrotechnic recall devices are still used in some places when the urgency of recalling divers outweighs the potential risks. They are also the primary method in various specialized dive environments where immediate, unmistakable signals are necessary. Military units, commercial dive operations, and some public safety teams dive in conditions where underwater situational awareness is often compromised, there’s no time to safely deploy other recall methods, and quick reaction capability is critical.

Divers must be briefed in advance on what primary and secondary systems are in use and how to respond when a recall device is activated. Misidentifying or ignoring the recall signal can lead to confusion and compromise safety. © Courtesy Ocean Technology Systems

Surface crews can signal divers by banging a dive weight, hammer, or screwdriver against a boat hull or dive ladder. Many divers report that it takes a while to register the recall, even when they expect it. © Stephen Frink

Acoustique

Les systèmes acoustiques de rappel utilisent des ondes sonores pour transmettre des signaux de la surface vers les plongeurs, permettant aux bateaux et aux équipes d’alerter ou de rappeler rapidement les plongeurs. Un haut-parleur sous-marin fixé à un câble pend dans l’eau à une profondeur optimisée pour diffuser le son. L’opérateur en surface peut transmettre différents motifs sonores, des signaux d’alarme, des messages préenregistrés, de la musique ou parler directement dans un microphone pour envoyer des commandes et avertissements.

Transmissions are loud enough that a hooded diver at several hundred feet can detect them. Divers do not need special electronic equipment to hear acoustic recall systems — the sound travels in all directions and is detectable by the naked ear.

The physical environment — such as bottom topography and composition, physical structures, and currents — can significantly affect an acoustic device’s performance. The projection range and message comprehension can be greatly reduced, so operators should account for background noise and seek to minimize it as much as possible.

Divers often report that exhalation noise often hampers finding the source of a sudden waterborne sound. When using recorded voice transmissions or speaking live to divers underwater, a siren or alert tone before the message can help get the divers’ attention and prepare them for the stated message.

Des tests intensifs montrent également que la répétition de phrases courtes et claires améliore grandement l’intelligibilité. Les plongeurs peuvent mal interpréter des commandes vagues ou des messages complexes si les instructions ne sont pas explicites.

It’s important for divers to observe a safety perimeter from the speaker as outlined in the unit’s operating manual. The dive operator should communicate this safe zone during the predive briefing. While these systems don’t cause anywhere near the physical discomfort level of a thunder flash or submarine sonar ping, these high-powered underwater audio transmission devices can cause permanent hearing loss or physiological damage if used inappropriately.

Conclusion

Diver recall systems allow dive operators to alert or recall divers in an emergency, but they do not eliminate the potential hazards inherent in diving or lessen the need for a thorough emergency action plan. It’s necessary to understand your recall system’s benefits and limitations and recognize if the dive plan includes elements that limit the capacity to quickly recall divers, such as decompression obligations or drift diving. Divers must be briefed in advance on what primary and secondary systems are in use and how to respond when a recall device is activated.

Mal identifier ou ignorer le signal peut mener à de la confusion et compromettre la sécurité. En cas de rappel, respectez votre vitesse de remontée et effectuez toutes vos obligations de décompression avant de faire surface.