Referring Clues

• Tin can's target
• German sub
• Sub
• Part of a wolf pack
• W.W. II predator
• W.W. II menace
• Depth charge target
• "Das Boot" setting
• One trying to avoid charges?
• German threat
• Sub that sank Allied ships
• Shipper's worry in W.W. I
• Wartime sea menace
• Sinker
• Member of a W.W. II wolf pack
• It may give a sinking feeling
• W.W. II sub
• German diver
• Wolf pack member
• W.W. II danger
• The Lusitania's undoer
• Lusitania sinker
• W.W. II vessel
• One in search of a tin can
• Q-ship's quarry
• Naval convoy menace
• Kriegsmarine vessel
• Ship sinker
• Liner threat, once
• Destroyer hunter
• Sub with sauerkraut?
• W.W. II blockade enforcer
• Torpedo launcher
• W.W. II German sub
• W.W. II Atlantic lurker
• Attacker of allied ships
• Part of a German naval fleet
• Ashcan's target
• Sinker of Allied ships
• WWII menace
• WWII sea menace
• Wartime sub
• Wolfpack member
• WWII submarine
• WWII convoy menace
• German WWII sub
• Nazi submarine
• WWI menace
• WWII sub
• Convoy raider
• WWII torpedo launcher
• Member of a wolf pack
• Sinker of the Lusitania
• German submarine
• Destroyer destroyer
• Subsurface war vessel
• WWII German sub
• WWII threat
• W.W. II sea menace
• Battle of the Atlantic vessel
• Axis submarine
• Vessel in "The Enemy Below"
• WWII ship sinker
• WWII vessel
• Athenia sinker
• WWII blockade vessel
• "The Enemy Below" threat
• WWII attacker
• WWI vessel
• WWII craft
• World War II sub
• WWII naval craft
• Maritime threat of the early 1940s
• WWII predator
• Destroyer's foe
• Erstwhile German marine menace
• "Das Boot," for one
• Marine menace
• German war vessel
• WWII maritime marauder
• German sea scourge
• WWII enemy sub
• WWII military transport
• Lusitania's undoing
• Lusitania undoer
• Lusitania's attacker
• Liner sinker
• "The Enemy Below" attacker
• WWI danger
• Concern for an Allied ship
• Kapitan's Command (hyhp)
• Kapitan's command
• WWII convoy raider
• Wolf pack member of WWII
• German military sub
• Underwater vessel
• "Das Boot," for one
• WWII ocean menace
• Lusitania's sinker
• Convoy chaser
• W.W. II ship sinker
• WWII German threat
• Convoy chaser
• Convoy chaser
• Convoy chaser
• Convoy chaser
• Former Atlantic ocean threat
• Kapitan's command
• Wolf-pack member
• Torpedo shooter
• World War II vessel
• Wolf pack vessel
• Sub of WWII
• WW II sub
• Sub in WWII
• German vessel in WWII
• Marine menace of WW2
• WW II shipping threat
• WWII maritime menace
• German menace
• WWII naval menace
• Axis predator
• Member of the Kaiser's fleet
• Certain torpedo launcher
• Part of Germany's World War fleet
• Maritime threat of WWII
• WWII undersea menace
• Depth-charge target of WWII
• Raider in the battle of the St. Lawrence
• See 7-Down
• WWII fleet
• Depth charge target of WWII
• "Das Boot" vessel
• German WWII threat
• World war II staple
• Threat to a WWII destroyer
• Depth-charge target
• WWII sea threat
• German WWII submarine
• Battle of the Atlantic craft
• Kaptain's command
• German craft
• Torpedo carrier
• Source of doom for the 17-Across
• WWII Enigma machine user
• Depth-charge target of old
• Destroyer downer
• WWI predator
• Battle of the Atlantic participant
• WWII movie staple
• See 23-Across
• W.W. II German vessel
• German lurker
• Dangerous sub of WWII
• Convoy menace of WWII
• Dangerous WWII sub
• Depth-charge avoider of WWII
• World war sub
• Submersible warship of WWII
• Former maritime menace
• Seagoing wolfpack unit
• Weaponized sub of WWII
• Sinker of sorts
• German submarine (hyph.)
• German WWII craft
• Submarine
• Vessel about to be broken up
• Vessel in the Kriegsmarine
• Its first letter stands for "untersee"
• A note about a snake
• About (anag)
• War vessel forbidden to come up to receive oxygen
• Stealthy WWII craft
• Avoider of charges?
• Part of a WWII fleet
• Vessel included in the so-called "Plan Z"
• Submarine about, at sea
• Worried about vessel
• Engineer about to reveal submarine
• Vessel wobbling about
• Marine menace of WWII
• Wartime menace about to be destroyed
• Sub of old
• WWII peril
• WWI craft
• Historic vessel just about wrecked
• WWII sea attacker
• One in a seagoing wolfpack
• WWII target
• Menace in the 1957 film "The Enemy Below"
• Destroyer sinker
• Old torpedo launcher
• Sub you can't eat
• Ashcan target, at sea
• Hamburger sub?
• Undersea WWII threat
• WWII naval threat
• Vessel about to be rebuilt
• Marine predator of old
• Depth charge sub, once
• Old marine menace
• Vessel just about wrecked
• Something forbidden by the Treaty of Versailles after W.W. I
• Wartime destroyer destroyer
• It's about wrecking a vessel
• WWII wolf pack unit
• Wolf pack vessel in W.W. II
• Kind of vessel apt to sink a lot
• Vessel of the World Wars
• In-depth subject for a war historian?
• WWII marine vessel
• W.W. II threat
• Threat to the Allies in W.W. II
• Vessel turning about?
• German sub in W.W. II fighting
• Menace in "Dead Wake: The Last Crossing of the Lusitania"
• German sub dangerous to Allied ships