Related Clues:

• WWII blockade vessel
• W.W. II Atlantic lurker
• WWII ship sinker
• Destroyer's foe
• German sea scourge
• W.W. II German sub
• Unterwasser vessel
• Erstwhile German marine menace
• Its first letter stands for 'untersee'
• W.W. II sea menace
• WWII maritime marauder
• Lusitania's sinker
• W.W. II threats
• ''The Enemy Below'' attacker
• Maritime threat of the early 1940s