Related Clues:
- Erstwhile German marine menace
- Its first letter stands for 'untersee'
- W.W. II sea menace
- WWII maritime marauder
- Lusitania's sinker
- Destroyer at sea
- ''The Enemy Below'' attacker
- Maritime threat of the early 1940s
- Sinker of the Lusitania
- Ruin, as plans
- Liner sinker
- WWI danger
- Sub in WWII
- Concern for an Allied ship
- Submarine weapon