Just came back from a long patrol with my shiny new VIIB (october '39) and a rather green crew.
It was rather boring since the weather was exceptionally crappy...
Anyway, while being on my way back, south of the shetlands, I spotted a small freighter chugging merrily right into a decent AOB.
Kaleun: Periscope depth!
Raised the periscope and started to take a bearing on the steamer.
I suddenly noticed my detection meter going red (yeah, I'm still using it...
). Since my sonarman didn't inform me on any other ships in the vicinity, I thought: "Well, must be a bug then".
Slowly moving into a perfect position to launch an eel, I suddelny heard high revving screw noises getting louder and louder.
Kaleun: What the...
*Spins periscope around*
Kaleun: ENEMY DESTROYER APPROACHING! ALAAAAAAAAARM! 
*chugga-chugga-Chugga-Chugga-CHUGGA-CHUGGA-SPLASH-SPLASH-SPLASH*
Bernard: Wasserbomben! 
Kaleun: 
Kaleun: Depth under keel?!?
NO: 80 meters!
Kaleun: 
Thank god the destroyer's crew must've been even dumber than my bunch o' twonks because they tossed the ashcans anywhere but not even close to my sub.
I quietly snuck away into deeper waters...
Memo to myself: Never -ever- trust the guy with the headphones.
