It is our opinion that on the evidence of the results obtained there is sufficient data to provide the following recommendations on the optimum type or combinations of diver location devices for prevailing environmental conditions from the most commonly used diving platforms, namely inflatable boats and hard boats. There is limited data from aerial relocations of devices. The Coastguard helicopter in Shetland was only utilised on a few occasions due to adverse weather. Aerial relocations are supported from the relocations made during the search exercise.
Folding flags with a day-glow yellow pennant are an exceptional location aid and are strongly recommended. This flag is highly conspicuous under a wide range of environmental conditions to all observers and was considered by far the most reliable and cost effective location device to be tested. Flags with red or orange pennants also perform well. The relocation potential of folding flags are optimised when observed from a diving support vessel, and maximised when the search aspect is abeam to the prevailing wind direction.
Divers undertaking diving operations during periods of low light intensity should always carry a high intensity and good quality strobe. Additionally, these strobes should always be attached in an elevated position, such as the top of a folding flag to afford the maximum location distance. Sealing surfaces and o-ring seals require regular inspection prior to use and based on our experiences we would recommend that two strobes be carried if this device is to be relied upon as a primary location aid.
The use of a torch as a location device is strongly recommended. The torch should be able to provide an intense beam for a suitable period of time. It is recommended that a reserve torch is available as a signalling device since a main light source used during the course of a dive may have a severely depleted power supply.
These devices are invaluable as location aids for particular diving techniques. In particular wreck, drift and decompression dives. These location devices should be as conspicuous as possible. If this device is sausage shaped, it should be wide and be able to provide a substantial height above sea level. Decompression sausages that can remain self-inflated will provide a more easily maintained form when the diver is on-surface for any length of time under adverse sea states. Equally, these devices will not deflate if incorrectly deployed. Decompression markers may provide increased location distances if they are manufactured in the same day-glow yellow colour as the folding divers flag.
A pair of suitably large Polyform buoys provides reasonable location distances. We would recommend that buoys be as large as possible, preferably 40 cm in diameter or larger. The separation distance between the buoys should be a minimum of two meters. This can provide increased location distances particularly when the search aspect is abeam to the prevailing wind direction. Divers using any marker buoy from which they may become separated should always carry a secondary device. A day-glow yellow folding divers flag would be a suitable device.
Pyrotechnics are not recommended for use by divers under a wide range of typical diving operations. Whilst they may provide substantial relocation distances, pyrotechnics are not specifically designed for excursion under water. These devices are relatively expensive and are not conveniently transported. The reliability of these devices after long term exposure in a marine environment is not known.
Marker dye is unsuitable as an aid for sea level location. It has however demonstrated a substantial location distance by aerial relocation. The marker dye must however be able to produce a very dense and prolonged release of dye to promote aerial observation. The Presto Dyechem marker dye produced an impressive slick of dye that was easily observed by helicopter.
A combination of location devices should be considered in many circumstances. Whilst folding flags and some decompression markers perform well under normal daylight and some intermediate light conditions, a device that can consistently promote location in low light and darkness will often be required. On the basis of our findings a combination of a folding flag (yellow pennant preferred) and strobe is recommended. The strobe should be placed in an elevated position, preferably attached to the top of the folding flag.
Our experience of device relocation over a protracted period found that the ability of individuals to relocate particular devices at, or close to sea level varies considerably. Similarly, we found this ability does improve for many observers after a frequency of device searches. Familiarity of the devices under a range environmental conditions, enhances the ability of observer to relocate them. Observers on board typical diver support vessels should ideally be competent in relocating location aids. Observers must be also aware of the location device/s carried by the diver/s at all times. This information may provide be an invaluable aid in those incidents where SAR facilities are required. As far as reasonably practicable, it is recommended that more than one observer should remain on a support vessel. If a dive plan assessment identifies a high risk of in-water divers becoming separated from the diving support vessel, particular consideration must be taken of the prevailing environmental conditions, the number of in-water divers at any given time, and the location devices that the divers should carry. Divers performing shellfish diving operations should always undertake a risk assessment on a daily basis taking the above factors into account with particular attention focused on the dive site, number of divers to be deployed and the separation distance of deployment.
It has been demonstrated that many devices are more easily observed from elevated platforms. Under many circumstances, elevated observation positions on hardboats do provide an enhanced relocation potential over inflatable boats. Observation platforms must also be considered in regard to the search capabilities of lifeboats or helicopters for diver location devices. Folding flags, plastic buoys, SMB sausages and bags were relocated by aerial observation, though no one consistently more so than another. Variations in search altitude, search aspect, and in particular the limited number of relocations that were undertaken, do not provide sufficient results to recommend the most suitable location aid for aerial relocation.