The death of a recreational diver during a dive of a sunken German battleship off the Orkney Isles was almost certainly the result of being struck by the propeller of a support boat, investigators have said.
The incident happened during a dive of the battleship SMS Markgraf, which lies at a depth of 45m in Scapa Flow, on the morning of September 28 2023.
On Thursday, the Marine Accident Investigation Branch (MAIB), whose probe into the incident is ongoing, issued a safety bulletin describing what happened and setting out a number of safety recommendations arising from it.
The document explains that the incident happened as the diver and their dive buddy were carrying out “decompression stops” as they were on their way back to the surface.
A decompression stop is the period a diver must spend at a relatively shallow constant depth while ascending from a dive, in order to avoid decompression sickness, more commonly known as “the bends”.
According to the bulletin, the pair had released their delayed surface marker buoy (DSMB), a floating marker that alerts people to a surfacing diver’s whereabouts, and that this was clipped to the casualty’s dive vest.
They were on their final decompression stop three metres below the surface when the diver was struck by the rotating propeller of the support boat Karin.
The bulletin said: “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 two-day air and sea search of the area was conducted, but without success.
“The missing diver’s body was found three 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.
The MAIB bulletin makes a number of safety recommendations in light of the incident, including the need for boat crews to maintain a lookout when operating in areas with people in the water and the need for them to maintain “detailed and frequent communication” with other boats in the same area.”
It also sets out the importance of using a DSMB correctly, explaining this should be held in the diver’s hand rather than attached to their body, as was the case with the diver in this incident.
The bulletin explained: “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.”
The MAIB investigation into this accident is ongoing and the body will publish a full report upon its completion.