"The Singing Sailor Underwater Defense System"

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  On the 27th of April, The Singing Sailor Underwater Defense System was installed into the sea in the archipelago due east of Stockholm. The Singing Sailor is a subsurface sonar system sending out the Morse code: "This way if you are gay". For any submarines passing close by, The Singing Sailor also features the message “Welcome to Sweden. Gay since 1944.” (the year Sweden legalized homosexuality) as an animated neon sign.
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http://www.svenskafreds.se/singingsailor/