My uncle was a TBF pilot with VC-19 in WWII (KIA). This led to an interest in sub hunting groups in the Atlantic, and through "Hunter-Killer" by William T. Y'Blood. His mention of the Fido Homing torpedo had me interested, especially since there were no photos or illustrations of the weapon in his book. A little looking, and here it is for those interested... The term "mine" was used to throw German intelligence off the track concerning the torpedo's true purpose. Excellent write up and description here: uboat.net - Fighting the U-boats - Technical pages