Plot hole: Maria describes in lurid detail how Anna was arrested by the Germans and tortured by being severely whipped, leaving her with gruesome scars all over her back. She also says that Anna hasn't spoken a word to anyone since she escaped from captivity. How, then, does Maria (or anyone else) know about the scars? Nobody saw them (they don't exist) and Anna obviously didn't tell anyone about them.
Plot hole: Whilst on the surface a drifting ship is seen and an officer and two sailors are sent to check it. On deck the officer says check fore and aft. The sailor who goes to the right and out of sight is back in 5 seconds. This is not enough time to check his allocated section. The script should have shown the officer check his watch (dial visible) and say something like "you have got 15 minutes". Next shot to show the officer checking his watch again and we see 10 minutes have passed and the men return.