During World War II, around 1940-1945, Sweden had a top-secret facility where seals were trained to locate enemy submarines and attach magnetic buoys with lights to them. The facility was classified as secret for 50 years, but is today open to the public.
https://sv.wikipedia.org/wiki/F%C3%B6rs%C3%B6ksstationen_Palmen
Posted by Randomswedishdude