In the early afternoon of 18 December 2011, the tug WESTSUND was towing the barge AARSLEFF JACK III on an easterly course in the South of Gedser Traffic Separation Scheme (TSS) in the western Baltic Sea.
During the towing operation one spud pile (barge leg) on the barge came loose, lowered itself, hit the seabed and broke off. Later that afternoon, another spud pile came loose and lowered itself to the seabed, resulting in the barge grounding. After an unsuccessful attempt to repair the jack-up unit holding the spud pile, the second spud pile including a pontoon broke off.
About three hours after the loss of the second spud pile, the container ship JOHANNA passed the area and collided with one of the spud piles. The spud pile penetrated the hull above the waterline and forecastle deck. The crew did not become aware of the damages until early next morning and JOHANNA diverted to the port of Karlskrona, Sweden, for repairs.
The report can be downloaded in PDF format here.