There was a spine chilling postscript to the story of the operation to move the German U-boat. Out beneath the dark waters of the Dover Strait a diver had come within a hairsbreadth of losing his life as he was dragged remorselessly into the blades of a rotating propeller.
The self-propelled crane barge M.V. "Norma" had located the submarine and dropped a marker buoy on a weighted line to mark its position. A diver was then sent down to replace the lightweight shot line with a heavy duty polypropylene rope.
Unbeknownst to the diving team, the vessels two propellers were still rotating. These were Voith Schneider propellers which are mounted horizontally. When the vessel is stationary, the propellers rotate continuously with the pitch of the blades in neutral. Movement of the vessel in any direction is controlled by varying the pitch on the propeller blades.
Prior to the diver entering the water, the Master had instructed the Second Officer on the Bridge over the walkie talkie to switch off the propulsion motors. The Second Officer was new to the ship. He switched off the Voith Schneider control panel on the Bridge but was unaware that this only switched off the pitch control and left the main motors turning the propellers in neutral.
The diver descended to twenty metres whereupon he felt himself being pulled by his umbilical cable, which had become entangled in one of the propellers. He asked to return to the surface but the diving team were unable to prevent the umbilical from running out and breaking. The diver managed to turn on his emergency air bottle but was rotating rapidly and unable to cut the umbilical which was dragging him inexorably into the propeller.
The diving team frantically contacted the Bridge who phoned the Engine Room where the Chief Engineer saw that the main motors were still running and threw the switches to stop them.
By this time the diver was within ten feet of the propeller blades and certain death. He thereupon managed to cut the umbilical and returned to the surface in a state of shock.
The vessel returned to Dover to clear the tangled cable from the propeller and is seen in the photo above berthed on the Eastern Arm the following day.
An investigation was carried out by the Marine Accident Investigation Branch and is available on their website at:
http://www.maib.gov.uk/publications/investigation_reports/2009/mv_norma.cfm 
