On the morning of 28 September 2023, a recreational diver carrying out decompression stops died, almost certainly as a result of being struck by the rotating propeller of the UK registered diving support boat Karin. The diver had been diving from a second dive boat that was also supporting divers exploring the wreck of the German battleship SMS Markgraf, which was lying at a depth of 45m in Scapa Flow, Orkney Islands, Scotland.

The key safety issues identified were:

• The need to maintain an effective lookout at all times while a vessel is underway is vital when operating near people in the water, such as around dive boats. Posting a dedicated lookout in an appropriate location is essential to make sure the helm/skipper receives timely warnings of surfacing divers and allow for effective avoiding action.
• The need for detailed and frequent communication between operators when multiple boats intend to operate in the same area. This coordination is crucial to ensure deconfliction and prevent accidents. 
• Following good practice guidance for correct handling of a delayed surface marker buoy (DSMB) by divers is essential. As recommended by the British Sub-Aqua Club (BSAC), divers should hold the DSMB line in their hand rather than attaching it to their person. This practice ensures that if the DSMB is snagged by a passing craft the diver can release the line to avoid entanglement and the risk of being pulled to the surface or into contact with the vessel.

Safety recommendations:

• The British Diving Safety Group is recommended to disseminate this safety bulletin to all organisations and agencies within its membership drawing attention to the safety issues raised, in particular:
• that owners, operators and skippers of diving support boats should ensure compliance with COLREGs Rule 5 concerning provision of a lookout, especially when operating in proximity to divers in the water.
• to raise awareness among its members of the hazards to divers of attaching a DSMB to their person while submerged, and that the recognised good practice is for the reel to be held in their hand.

On the morning of 28 September 2023, a recreational diver carrying out decompression stops died, almost certainly as a result of being struck by the rotating propeller of the UK registered diving support boat Karin. The diver was diving from a second dive boat that was also supporting divers exploring the wreck of the German battleship SMS Markgraf which was lying at a depth of 45m in Scapa Flow, Orkney Islands, Scotland.

The diver and their dive buddy had ascended to their final scheduled decompression stop 3m below the surface. The divers were conducting a drift decompression away from the available shot line1 but their presence was indicated by their delayed surface marker buoy (DSMB)2, the line of which was clipped to the casualty’s dive vest. The DSMB was visible to the second dive boat waiting on the other side of the wreck site, but it was not sighted by Karin’s crew before Karin motored over it. The crew of the second dive boat saw the DSMB disappear under Karin. Subsequently, one of the two divers failed to resurface.

The coastguard was notified and an extensive 2-day air and sea search of the area was conducted, but without success. The missing diver’s body was found 3 weeks later following a seabed search conducted by a local survey vessel using side-scan sonar. A specialist team recovered the diver’s body from the seabed.

Karin was a 24m converted fishing boat with a draught of 2.8m, certified by Mecal Ltd under the Maritime and Coastguard Agency’s (MCA) Small Commercial Vessel and Pilot Boat Code of Practice (SCV2), annexed to Marine Guidance Note (MGN) 280 (M). The two crew of Karin comprised a skipper, who was suitably qualified and had extensive experience both as a diver and dive boat skipper engaged in this type of operation, and a crew member whose principal role was that of cook.

The accident occurred during daylight in favourable environmental conditions with good visibility, calm seas, no rain, and a tidal stream of less than 1 knot (kt). Karin was manoeuvring at a speed of 4kts slightly to the east of the shot line marking the stern of the wreck. The tidal streams in the area were not strong, although it was not uncommon for divers to carry out drift decompression stops before surfacing. The DSMB marking the casualty and their buddy had been on the surface for 11 minutes before the accident, but had not been seen by Karin’s skipper who was operating the boat from the wheelhouse during this time.