This was a British midget submarine attack on the harbour of Bergen in German-occupied Norway (14/15 April 1944).
The operation was originally to have been carried out by X-22, but this boat was accidentally rammed while training and lost with all four hands, so X-24 under the command of an Australian officer, Lieutenant M. H. Shean, was tasked with the destruction of the Laksevåg floating dock at Bergen. The boat was towed across the North Sea by the submarine Sceptre, and successfully entered Bergen harbour. The boat laid its charges under what its captain though was the floating dock, but was in fact the 7,569-ton merchant vessel Bärenfels lying alongside the floating dock. The ship was sunk but the dock suffered only minor damage, and X-24 escaped without damage and after a long exit rejoined the Sceptre off the Norwegian coast to be towed home.
The Germans attributed the sinking of the coal transport Bärenfels to sabotage.