In the early 1970's, the U.S. government learned of the existence of an undersea cable running parallel to the Kuril Islands chain, connecting the major Soviet naval bases at Vladivostok and Petropavlovsk.Also this related, lighthearted tale from < a href="http://spookgroup.tripod.com/id8.html">Spookgroup:
[A] joint Navy-National Security Agency (NSA) mission was initiated, code-named Operation Ivy Bells, involving the use of U.S. Navy fast attack submarines working in conjunction with specially-trained Navy combat divers. Working in tandem, they would make monthly incursions into these dangerous waters to "tap" the line.
Once the device was in place, subsequent missions were required in which a submarine would return to the location to pick up the six to eight weeks' worth of recordings inside the pod. For this operation, the frogmen would depart the sub's escape trunk, swim to the cable (reportedly with the aid of a minisub on occasion), remove the recorded tape, and then make their way back to the waiting submarine. This tape was then delivered to the NSA for processing and dissemination to the appropriate military and civilian agencies. Not long after the recovery of the first tapes, it was discovered that the Soviets felt so sure of the security of their undersea communication line, that the majority of the concersations recorded were completely uncoded!
From LCDR(Ret) John Arnold
On Halibut, after our 2nd back-to-back Ivy Bells mission, my 4 Chiefs were bored and up to mischief on our return to CONUS. They stole the CO's stateroom door. The CO had the XO's door transfered to his stateroom & told the XO he didn't care if they ever found the door. Needless to say the XO was ticked. Each watch section had a search/recovery team looking in vain for the elusive door. To add insult to injury, the spook Chiefs re installed the (missing for 10 days) door on the XO's stateroom. All of this accomplished without discovery or even a clue as to who pulled off this great TF. It wasn't until our mission debrief at NSA that we revealed the Mystery to the skipper-Chuck Larsen. I've heard that other ships have tried this but the door has always been found and many times the culprit is caught in the act of removing the door. These guys were a cleaver team aside from providing NSA with hundreds of the finest broadband tapes that they had ever received!