The impact popped the bow door open, allowing a rush of sea water into the car deck.
It was caused by a crew member forgetting to close the bow doors of the ferry.
He said there was some evidence that the bow door was wide open or missing by the time the ship went down.
Finally the bow doors were sealed, as they would no longer be needed.
The ship put to sea with its bow doors open.
Waiting to close bow doors before leaving port eats into profits.
Blame for that accident was placed on personnel who failed to close bow doors.
An investigation blamed "an inrush of water through open bow doors" as the cause.
The vessel had 463 passengers and crew on board when it left the port with its bow doors still open.
She closed her bow doors at 00:05 on 8 July 1944.