I have divers down - got my drift?

Communication and signalling during diving operations

A charter boat was engaged in diving operations off the west coast of Scotland. It was daylight and, in accordance with the Collision Regulations, she was exhibiting a rigid replica of the International Code flag "A" to indicate that she had divers down and was therefore restricted in her ability to manoeuvre.

The weather was calm with clear visibility, and a southerly tidal stream of about 0.3 knot was running. Four pairs of divers and one group of three had dived on to a wreck by means of a shotline, which was marked with a buoy displaying Code flag "A".

The first pair of divers to surface was picked up at the shotline. Two delayed surface marker buoys (DSMBs) then broke the surface and started to drift in a southerly direction with the tide. These buoys indicated that two groups of divers were in the process of surfacing. The charter boat initially maintained position between the shotline buoy and the DSMBs, and then moved to the shotline as a second pair of divers surfaced. Having picked up the second pair, the boat returned to a position midway between the shotline buoy and the DSMBs.

At this time, the skipper noted a ferry approaching from the north and a yacht approaching from the south. One of the two DSMBs was used by the group of three divers, who then surfaced and were picked up, informing the skipper that the pair using the remaining DSMB still had approximately 10 minutes of decompression stops to perform. The skipper called the ferry on VHF radio to draw her attention to the shotline marker buoy, but received no reply.

The penultimate pair of divers then surfaced at the shotline buoy. Having estimated that the yacht would pass well clear of the DSMB on her current heading, and uncertain as to the ferry's intentions, the skipper decided to return to the shotline buoy. At this point, the final pair of divers surfaced and, using hand signals, acknowledged the skipper's intention of proceeding to the shotline before returning to pick them up.

Having picked up the penultimate pair of divers at the shotline buoy, the charter boat headed towards the last pair. The approaching yacht's skipper, having not yet sighted the DSMB, and interpreting that a risk of collision now existed with the charter boat, altered course to starboard towards the DSMB. However, on sighting the DSMB ahead, he altered course to port and passed about 100 metres from the divers, as they were being picked up from the water.

The Lessons

1. Both the ferry and the yacht were required under the Collision Regulations to keep out of the way of the charter boat. It was a clear day and the boat was exhibiting a rigid replica of the International Code flag "A", which served to indicate two things:

• she was a vessel restricted in her ability to manoeuvre; and
• she had divers down, requiring approaching vessels to keep clear at slow speed.

In the event, both the ferry and the yacht kept clear of the charter boat. However, the yacht's skipper did not appreciate that divers were located some distance from the charter boat. Hence, in altering course to avoid what he considered was a risk of collision with the charter boat, he unwittingly headed towards the remaining pair of divers. In the event, he sighted the DSMB and the divers in sufficient time to be able to pass well clear.

This incident highlights the importance of those engaged in diving operations ensuring they exhibit clear signals, and those who are likely to be affected by them ensuring they interpret those signals broadly. In other words, as with all operations that effectively restrict a vessel in her ability to manoeuvre, they need to consider the likely extent of those operations, particularly in view of the prevailing weather and tidal conditions. Keep well clear means just that!

2. In this case, the charter boat's skipper at no time considered that the approaching yacht posed a danger to those in the water. However, in situations where safety margins are significantly reduced, consideration needs to be given to the fact that those in charge of approaching vessels may not appreciate the extent to which divers might be operating remotely from the charter boat. In such circumstances, greater attention should be paid to ensuring that the scope of operation is clearly identified and broadcast either on VHF Channel 13 or following an all stations VHF DSC safety alert. Similarly, those who approach an area in which diving operations are known to be taking place, and are unsure of the likely extent of those operations, should not hesitate to contact the charter vessel or the local coastguard station for more information. If you want others to know what you're doing - tell them. If you want to know what others are doing - ask them!

Reproduced by kind permission of the Marine Accident Investigation Branch. Originally published in MAIB Safety Digest 3/2003. www.maib.dft.gov.uk