Diver Location Aids: HSE Report


A range of devices are suitable for use as diver location devices. Some devices have consistently demonstrated greater relocation distances than others. There are many factors that must be taken into account in the process of selecting an appropriate device. The potential relocation distance of any device is only one consideration. The choice of location device in many circumstances is dictated by the particular scope of the diving operation. Delayed SMB's are certainly required when divers plan to undertake scheduled decompression stops. They should also be considered as a device to be available should unplanned decompression stops be required. Particular environmental conditions relevant to the type of diving, such as drift diving, require the use of a permanent surface-marking device such as a self-deploying SMB. This marker buoy should be capable of remaining inflated and should be as large and as conspicuous as possible. The use colours other than red or orange should always be considered.

The folding divers flags have demonstrated excellent relocation capabilities and should be considered an invaluable location device for divers on-surface. They are relatively cheap and are extremely robust and reliable. They provide a suitable elevation to enhance relocation of the diver from diving support vessels. These devices are also located by helicopter but less readily so than from vessels. They are conveniently stowed to the side of the scuba set by attaching to the cylinder with elasticated straps. A variety of diver location devices have been trialed by recreational divers. The Dorset Diving Sub-Aqua Club amongst others, conducted a series of limited trials in collaboration with the Royal Naval Air Station at Portland. A selection of location devices was assessed and their relative merits and limitations highlighted. It was concluded that the folding divers flag was the best location device tested.

Working shellfish divers have commented that the colour and size of buoys affects ease of sighting under particular light conditions and sea states . The results of this research suggest that this is certainly the case in many instances. Plastic buoys commonly used as markers vary in colour. We have found that red and orange does become more difficult to locate than brighter day-glow colours in low light conditions. On the basis of our findings there is good support for the use of buoys as SMB's for shellfish divers that are as large as may practically be used. The use of paired buoy combinations is also considered to provide enhanced location over single buoys. An adequate separation distance between buoys also facilitates their relocation potential under particular search aspects. Guidance notes for commercial shellfish diving projects have been previously issued by the Health and Safety Executive. This guidance recommends that the divers are 'equipped with a means of emergency location such as flares, strobe light, high visibility flag or a combination of these . Divers undertaking this scope of work should consider an emergency location device that is both durable and reliable under the rigours of heavy daily use, additional to the marker buoys on shotlines.

Any electrical device that is intended for use in a marine environment, and those particularly designed to withstand hydrostatic pressures must be reliable. Diver's torches have evolved over many years and there are now many high quality reliable torches on the market. The reliability of these devices in the long term is often aided through regular and thorough inspection and maintenance. Particular attention must always be given to sealing surfaces and o-rings. In our experience of many types of waterproof housings, a seal is often made with only one o-ring against a flat sealing surface. University staff have frequently used strobes during the course of normal diving operations and have found that high quality strobes are as prone to the ingress of water as lesser quality strobes. The operator can only endeavour to use these devices according to the manufactures instructions and pay particular vigilance to seals. The reliability of these cases could be greatly improved by manufacturers incorporating two independent seals.

During the course of the initial relocation exercises it was apparent that the ability to relocate devices varied considerably between observers. Some observers consistently located all devices at significantly greater distances than others. Those observers that that were considered to be weaker at locating the devices did improve during the course of the trials. This is most easily attributed to a steadily improving search ability and familiarity of the device aspect in relation to observation height and the prevailing environmental conditions. This individual ability to relocate particular devices must be considered an important factor in complementing the location properties of any device. Individual observers who consistently recorded lower sighting distances after a protracted period of search exercises may be accounted for by differences in eyesight. For some divers, skippers and boat crews, visual impairments may have a profound effect on the ability to relocate those devices that require visual sighting in respect to colour and distance.

HM Coastguard is the authority responsible for the initiation and co-ordination of Civil Maritime Search and Rescue. This includes responding to calls for assistance from divers and diving craft. On conclusion of any diving related incident, the Coastguard Maritime Rescue Co-ordination Centre (MRCC) responsible for co-ordinating the incident forwards an incident report to the National Diving Liaison Officer (NDLO) to extracts details of each incident. The summary of these incidents between 1996 and 1997 indicates 42 incidents of missing/lost divers, representing 22% of all incidents. During 1998, these incidents numbered 33 (17% of all incidents). Engine failure represented 12% (1997) and 12.5% (1998) of all incidents . The number of 'missing diver' incidents is likely to be much higher than reported. A 'missing diver' should be regarded as all instances that involve an initial inability to relocate the diver. These incidents are likely to be unreported in the first instance until a preliminary search has been made. In many instances divers are temporarily lost and subsequently relocated in a relatively short period. However, it is not uncommon for calls for assistance from the Coastguard. In some cases large scale search and rescue (SAR) facilities are required to relocate divers.

Divers undertaking decompression stops for significant lengths of time can drift considerable distances. Suitable decompression markers allow the boat to mark a divers position as the diver remains submerged. Variations in the direction and rate of tidal movement can separate and carry divers considerable distances. The majority of divers are conscientious regarding adjustments to diving schedules and procedures in accordance with changing weather and sea conditions in order to minimise this risk. There are however many occasions when this is not the case, and divers have been 'lost or misplaced' for significant lengths of time whilst the diving vessel searches in what is judged to be the most likely direction of drift.



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